The IMO Passage Planning Model: Appraise, Plan, Execute, Monitor
IMO Resolution A.893(21) established the four-phase model as the international standard for passage planning. Every commercial vessel is required to follow this model. The USCG exam tests all four phases and their specific content requirements.
Gather ALL relevant information before drawing a single waypoint. This phase is the foundation — everything built on incomplete appraisal is flawed.
- ►Obtain current charts at appropriate scale for the entire route
- ►Review Sailing Directions, Coast Pilots, and Light Lists for the region
- ►Identify all navigational hazards, restricted areas, and no-go zones
- ►Research the vessel's capabilities: max draft, beam, air draft for bridges
- ►Gather weather pattern information for the season and expected passage window
- ►Identify all ports of refuge along the route
- ►Research customs, immigration, and clearance requirements at destination
Translate the appraisal into a detailed, written passage plan. Vague plans cause accidents. The plan must be specific enough that any qualified officer can execute it.
- ►Plot all waypoints with latitude and longitude coordinates
- ►Record courses and distances between each waypoint
- ►Mark all hazards, shoals, and no-go zones on charts
- ►Calculate tidal windows for critical passages and tidal gates
- ►Determine fueling stops and calculate fuel budget with reserve
- ►Draft crew watch schedule and rest hour compliance
- ►Prepare communications plan with radio check-in times
Carry out the plan. The master briefs all officers and crew. Deviations from the plan must be communicated to the master and documented in the log.
- ►Master briefs all officers on the passage plan before departure
- ►Officers of the watch understand and follow the plan as written
- ►All deviations are reported to the master and logged
- ►Safety equipment checks are completed before clearing the harbor
- ►Pre-departure checklist is signed and filed
- ►Float plan filed with responsible party ashore
- ►Initial radio check-in completed on departure
Continuously compare actual position against the planned track. Conditions change — the plan must be revised when reality diverges significantly from the plan.
- ►Fix position at regular intervals using multiple methods
- ►Compare actual track against planned track — note set and drift
- ►Update ETA at each waypoint and for port of arrival
- ►Monitor weather continuously and compare to forecast
- ►Update fuel remaining against consumption predictions
- ►Log all watch changes, positions, and significant events
- ►Revise plan when conditions require — document the revision
Chart Selection and Correction
Using the correct chart scale is a foundational navigation skill. A chart that is too small in scale misses critical detail in confined waters. A chart too large in scale makes ocean planning impractical. Every chart must be current and corrected before being used for passage planning.
Small-Scale Charts (1:500,000 and smaller)
Ocean and coastal passage planning; overview of large geographic areas
Show broad coastlines, major shipping lanes, offshore hazards, and ocean depth contours. Used for appraisal and initial planning of offshore routes.
Example: NOAA Chart 13003 — Gulf of Maine (1:400,000)
Medium-Scale Charts (1:80,000 to 1:500,000)
Coastal passage planning; harbor approaches
Show major coastal features, principal harbors, offshore hazards in useful detail. Used for plotting offshore waypoints and monitoring the passage track.
Example: NOAA Chart 12200 — Chesapeake Bay (1:200,000)
Large-Scale Charts (1:50,000 and larger)
Harbor EntryHarbor entry, anchorage, and pilotage in confined waters
Show detailed depth soundings, aids to navigation, restricted areas, and mooring facilities. Essential for port entry planning and navigation in unfamiliar harbors.
Example: NOAA Chart 18449 — Puget Sound, Northern Part (1:40,000)
Gnomonic Charts
Great circle route planning for ocean passages
Projects the earth so that great circles appear as straight lines. A straight line drawn on a gnomonic chart is the great circle route. Points along that line are then transferred to Mercator charts as waypoints for actual navigation.
Example: NOAA Pilot Chart — North Atlantic
NOAA Chart Correction Sources
- ►Notice to Mariners (NtM) — published weekly by NAVCEN; corrects nautical charts, Coast Pilots, and Light Lists. Essential for keeping paper charts current.
- ►Local Notice to Mariners (LNtM) — issued by each USCG district for temporary changes in their area. Check before any coastal passage.
- ►NOAA Print-on-Demand — charts printed from current digital files include all corrections through the print date.
- ►USCG Broadcast Notice to Mariners — urgent corrections broadcast on VHF Ch 16 and marine radio. Time-sensitive safety information.
Chart Correction Procedure
- Note the chart edition date and the date of last correction on the chart margin
- Download all NtM editions since the last correction date from NAVCEN
- Apply each correction with a fine-tipped pen — note the NtM edition number applied
- Record the correction in the chart's correction log on the chart margin
- On chartplotters: update the electronic chart cartridge or download the latest ENC
- Cross-check: electronic and paper charts should agree on critical features
Route Planning: Waypoints, Rhumb Lines, and Great Circles
Route planning converts a general intent to travel from point A to point B into a specific, navigable plan with defined positions, courses, and safety margins. Each element of the route has a purpose and a consequence if done wrong.
Waypoints
Specific latitude/longitude coordinates that define the route. Each waypoint should be at a course change, a navigational hazard, a tidal gate, or a point of significance. Waypoints must clear all hazards by an appropriate safety margin — never place a waypoint on a shoal to make the chart look clean.
Know: waypoints are programmed into the GPS/chartplotter and monitored against the paper chart plan.
Safety Margins
Each waypoint and leg must have a defined cross-track error limit — the maximum allowable distance the vessel can deviate from the planned track before corrective action is required. Safety margins account for GPS accuracy, current set, helmsman error, and the distance from hazards.
Know: safety margins must be greater than the sum of position error and closest hazard distance.
No-Go Zones
Areas explicitly marked on the chart plan where the vessel must never enter regardless of circumstances. Examples include shoal water, restricted military zones, marine protected areas, and traffic separation scheme (TSS) wrong-way lanes. No-go zones are often highlighted in red on paper charts.
Know: no-go zones must be marked before the passage begins, not discovered during execution.
Wheel-Over Points
The point at which the helmsman must begin turning to achieve the new course at the waypoint. Vessels with large turning radii (especially commercial ships) must begin a turn well before the waypoint. For an offshore yacht, wheel-over points are less critical but still matter in confined channels.
Know: larger vessels begin turns before the waypoint — not at it.
Abort Points
Pre-determined positions along the route where the captain will make a go/no-go decision to proceed or divert. For example, a point offshore where the weather has deteriorated beyond acceptable limits — the passage plan should define what weather criteria trigger a diversion at each abort point.
Know: abort points and go/no-go criteria must be defined in advance, not improvised offshore.
Rhumb Line vs. Great Circle: Side-by-Side Comparison
| Characteristic | Rhumb Line | Great Circle |
|---|---|---|
| Appearance on Mercator chart | Straight line | Curved line bowing toward nearest pole |
| Appearance on gnomonic chart | Curved line | Straight line |
| Course | Constant bearing throughout | Bearing changes continuously |
| Distance | Longer than great circle (except on equator) | Shortest distance between two points |
| Practical use | Short passages; coastal navigation | Transoceanic passages at higher latitudes |
| Steering | Simple: one course setting | Requires course updates or intermediate waypoints |
| Where the same | On the equator and on meridians | On the equator and on meridians |
Weather Routing for Offshore Passages
Weather is the single largest variable in offshore passage planning. A well-routed vessel avoids the worst conditions; a poorly-routed vessel encounters them at sea with no options. Weather routing is not optional for offshore — it is part of the IMO appraisal and plan phases.
See also our companion guide: Marine Weather Routing for Captains for detailed coverage of synoptic forecasting, GRIB files, and routing software.
Obtain Multiple Forecasts
Never rely on a single weather source. Cross-reference NOAA text forecasts, synoptic charts, GFS and ECMWF model runs, and routing-specific services. For passages over 48 hours, obtain a marine weather briefing from a professional router.
Identify the Systems
Locate all fronts, low-pressure centers, and high-pressure ridges on the synoptic chart. Determine their forecast tracks and intensities. Fronts generate the most dangerous offshore conditions — a fast-moving cold front can bring winds from zero to 40 knots in under an hour.
Define Go/No-Go Criteria
Before departure, the captain must define in writing the conditions that will abort or delay the passage. Common criteria: sustained winds over a set limit (e.g., 25 knots for a given vessel), wave heights over a set limit, tropical storm within a set distance. These criteria must be agreed before departure — not negotiated mid-passage.
Route Around Systems
Plan the route to stay in favorable wind quadrants of high-pressure systems and away from fronts. For tropical avoidance, maintain a minimum 500nm distance from tropical storms and 300nm from tropical depressions. Routing around the south side of a high in the North Atlantic gives favorable westerly winds; routing north puts you in headwinds.
Monitor and Revise
Download updated model runs daily during the passage. Compare model consensus — when GFS and ECMWF agree, confidence is high. When they diverge, assume the worst case. Update the passage plan when forecasts change materially. Document all weather-driven course changes in the log.
Tropical Avoidance Rules
- ►Maintain 500 nm minimum distance from any tropical storm (34+ knot winds)
- ►Maintain 300 nm from tropical depressions — they can intensify rapidly
- ►Atlantic hurricane season: June 1 through November 30
- ►Eastern Pacific season: May 15 through November 30
- ►Monitor NHC advisories every 6 hours during tropical season
- ►If caught in deteriorating conditions, the dangerous semicircle is to the right of the storm track in the Northern Hemisphere
Go/No-Go Decision Criteria (sample)
Define these criteria before departure — not offshore
- ►Sustained winds forecast to exceed 25 knots within 24 hours of departure
- ►Significant wave height forecast to exceed the vessel's comfort rating
- ►Fast-moving cold front expected to arrive during the passage window
- ►Named tropical system within 500 nm of the route
- ►Crew experience insufficient for forecast conditions
Tidal Planning: Gates, Tables, and Timing
Missing a tidal window offshore can mean extra hours or days at sea. Missing one at a tidal gate can mean dangerous conditions or grounding. Tidal planning is not guesswork — it requires the correct tables and the correct corrections.
Tide Tables vs. Current Tables
CriticalTide tables give the height of water above chart datum at a specific station. Current tables give the speed and direction of tidal flow at a specific station. They are different publications and sometimes different locations. High tide does not necessarily correspond to the maximum flood current — there is a lag. Passage planning requires both.
Tidal Gates
CriticalA tidal gate is any constriction where tidal current is strong enough to materially affect transit time or safety. Classic examples include Cape Cod Canal (max 4.5 knots), Deception Pass, WA (up to 8 knots), Hell Gate, NY, and most inlet entrances on the Atlantic and Gulf coasts. Missing a tidal gate window can mean waiting 6 to 12 hours for the next opportunity.
Rule of Twelfths
Tidal height changes unevenly through the tidal cycle. The rule of twelfths approximates the change as: 1/12 in the first hour, 2/12 in the second, 3/12 in the third, 3/12 in the fourth, 2/12 in the fifth, and 1/12 in the sixth. This means the tide moves fastest in the middle two hours and slowest near high and low water. Use this rule to estimate depth at any point in the tidal cycle.
Spring vs. Neap Tides
Spring tides (not related to the season) occur at new and full moon when the tidal range is greatest — roughly 20% above mean range. Neap tides occur at quarter moons when the range is smallest. A tidal gate that is manageable at neaps can be dangerous at springs. Passage timing must account for the phase of the moon and whether spring or neap conditions apply.
Datum and Chart Depths
CriticalNOAA charts use Mean Lower Low Water (MLLW) as the chart datum — the approximate lowest water level. Depths on the chart represent the depth at MLLW. Actual depth at any moment equals chart depth plus tide height above MLLW. In tidal gates and shoal channels, confirming actual depth at the planned transit time is essential.
Current Corrections
Current tables list data for reference stations. Secondary stations nearby require applying a time difference and speed ratio correction from the table. These corrections can be plus or minus several hours. Using the reference station time at a secondary location is a common and potentially dangerous error.
Rule of Twelfths — How to Use It
If the tidal range at a station is 6 feet, the tide rises and falls according to these proportions per hour from low or high water:
Example: Low water at 06:00, high water at 12:00 (6-hour range), tidal range 6 ft. At 08:00 (2 hours after low), the tide has risen 1/12 + 2/12 = 3/12 = 1.5 ft above low water. Depth at that time = chart depth + 1.5 ft.
Offshore Fuel Planning
Running out of fuel offshore is not a minor inconvenience — it is an emergency that can leave the vessel powerless in shipping lanes, heavy weather, or far from assistance. Fuel planning requires actual measured consumption data, not manufacturer estimates.
Step 1: Establish Consumption Rate
Run the engine at planned cruising rpm for one hour and measure fuel consumed. Do this in calm conditions to get a baseline. Most gasoline engines burn 1 gallon per hour per 10 hp at cruising load. A 200 hp engine at 70% load burns approximately 14 GPH. Diesel engines are more efficient — roughly 1 gallon per hour per 18-20 hp. Record the actual measurement for your specific vessel and rpm.
Step 2: Calculate Passage Fuel
Multiply consumption rate by estimated passage hours. Use realistic speed estimates — headwinds and seas reduce speed by 20-40%. A passage planned at 8 knots that encounters a 2-knot adverse current actually makes 6 knots, increasing time by 33% and fuel by 33%.
Step 3: Add Reserve
Add a minimum 10% reserve for an offshore passage. Add 20-25% for passages with limited fuel availability or uncertain weather. Some jurisdictions and insurance policies require a specific reserve. The reserve is not to be consumed except in genuine emergency.
Step 4: Identify Fuel Sources
Chart every marina, commercial fuel dock, and fuel cache along the route. Note opening hours, depth of approach, fuel type (gasoline vs. diesel), and whether credit cards are accepted. In remote cruising grounds, fuel may only be available at specific intervals — plan accordingly.
Step 5: Monitor En Route
Log fuel remaining at each waypoint or at regular time intervals. Compare actual consumption against the plan. If consuming faster than planned, revise speed, ETA, and fueling stops accordingly. Never assume fuel consumption will improve — plan for it to stay the same or worsen.
Fuel Reserve Requirements
- ►Minimum 10% reserve above calculated passage fuel
- ►20-25% for passages with limited fuel availability
- ►Rough seas increase consumption by 20-40%
- ►Headwinds and adverse current reduce speed; increase time and fuel
- ►Never consider reserve as available fuel unless genuine emergency
Speed vs. Range Tradeoffs
- ►Most displacement hulls have optimal range at hull speed or slightly below
- ►Planing hulls burn dramatically more fuel above threshold rpm
- ►Reducing speed by 10% can increase range by 20-30% on planing hulls
- ►Know your specific vessel's range-power curve before any offshore passage
- ►Fuel transfer from reserve tanks: test transfer pump before departure
Offshore Watch Systems and Rest Hour Compliance
Fatigue is the leading cause of offshore casualties. Watch schedules are not administrative paperwork — they are the primary fatigue management tool. A watch schedule that looks acceptable on paper but leaves crew chronically under-rested is a hazard, not a plan.
Three-Watch System (Traditional)
Six or more crew membersFour hours on, eight hours off
Swedish Watch System
Four to six crew membersAlternating three-hour and six-hour watches rotating daily
Two-Watch System (Doublehanded)
Two to three crew membersFour hours on, four hours off — or six on, six off
STCW Rest Hour Compliance
Required for all commercial vessels subject to STCWMinimum 10 hours rest in any 24-hour period; 77 hours in any 7-day period
Fatigue Management Best Practices
- ►Define watch schedule before departure — not underway
- ►Allow off-watch crew to sleep without interruption except genuine emergency
- ►Night watches are harder — assign the most experienced helm to 0200-0600
- ►A fatigued helmsman steering by compass will wander 20+ degrees — check often
- ►Log watch changes and any deviations from the plan
- ►On two-watch (doublehanded) passages over 48 hours: plan a port stop for rest
- ►Autopilot does not replace lookout — someone must monitor radar and horizon
- ►COLREGS Rule 5: every vessel shall maintain a proper lookout at all times
Offshore Communications Plan
A communications plan defines how the vessel will send and receive information throughout the passage. It covers routine weather downloads, position check-ins, emergency communications, and the float plan filing.
For GMDSS sea area definitions and equipment requirements, see also: Search and Rescue Operations.
VHF Radio (Fixed and Handheld)
Line of sight — approximately 25-40 nm vessel to vessel; 40-60 nm to a high-elevation coast stationEssential for all coastal passages and harbor operations. Required by law on US-inspected vessels. Channel 16 is the international distress and calling frequency — monitored 24/7.
Channel 16 must be monitored at all times while underway. DSC VHF requires MMSI number programmed.
SSB/MF-HF Radio
Hundreds to thousands of miles depending on frequency and propagationUsed for weather downloads via Weatherfax or SailMail (Pactor modem), position check-ins with maritime net (e.g., Herb Hilgenberg), and long-range voice communications. Requires a Ship Station License and operator certificate.
SSB allows email via Pactor modem — a key offshore weather tool. Frequencies vary by time of day due to ionospheric propagation.
Satellite Phone (Iridium, Inmarsat)
Global coverage (Iridium uses LEO satellites; Inmarsat uses GEO)Iridium provides true global coverage including polar regions. Inmarsat has gaps above 70 degrees latitude. Used for voice calls, text, and data. Critical backup when SSB propagation is poor.
Satellite communication is not a GMDSS substitute but is a valuable redundancy layer.
EPIRB (Emergency Position Indicating Radio Beacon)
Detected by COSPAS-SARSAT satellite system; alert relayed to USCG rescue coordination centers406 MHz EPIRB is mandatory for GMDSS compliance offshore. Must be registered with NOAA. Contains GPS for precise location data. Has a hydrostatic release for automatic float-free deployment if vessel sinks.
Registration is the captain's responsibility. An unregistered EPIRB delays rescue. Check battery and hydrostatic release expiry annually.
SART (Search and Rescue Transponder)
Detected by radar-equipped vessels and aircraft within approximately 8-10 nmWhen activated, transmits a distinctive radar return that appears as a line of 12 dots on any X-band radar screen. Used to guide rescuers to a survival craft. AIS-SART sends a digital AIS target instead of a radar signal.
Recognize the SART radar display pattern: 12 dots radiating from the SART position.
Float Plan
Filed ashore — no transmission rangeNot required by law but essential practice. Filed with a responsible party ashore who knows when to call USCG if the vessel is overdue. Must include: vessel description, MMSI, intended route, crew manifest, departure and expected arrival times, and contact information.
Float plans are the single most effective tool for ensuring rescue response if the vessel is overdue.
Sample Communications Schedule
| Time (UTC) | System | Purpose | Frequency / Method |
|---|---|---|---|
| 0000 daily | SSB / SailMail | Weather download (GRIB/Weatherfax) | Varies by time/frequency |
| 0800 daily | VHF Ch 16 | Watch commencement; monitor for traffic | Ch 16 continuous |
| 1200 daily | SSB / float plan | Position report to shore contact | Prearranged frequency |
| 1800 daily | SSB / SailMail | Weather download; update ETA | SailMail request |
| As needed | Satellite phone | Urgent communications; medical | Direct dial |
| Emergency | VHF Ch 16 MAYDAY / EPIRB | Distress communication and location | Ch 16; 406 MHz |
Pre-Departure Safety Equipment Checks
Every offshore passage begins with a safety equipment check. Expiry dates matter. An EPIRB with a dead battery or a life raft with an overdue service date is not safety equipment — it is false confidence. Check dates; replace or service as needed.
- ►Service date current — most require annual or biennial inspection by certified facility
- ►Hydrostatic release inspected and operating — releases automatically at 10-15 feet underwater
- ►Painter line attached to a strong point and accessible for manual deployment
- ►Container (valise or canister) shows no damage, cracks, or UV degradation
- ►Location known to all crew and accessible without tools
- ►EPIRB mounted adjacent to life raft for deployment together
- ►Registered with NOAA — verify registration at beaconregistration.noaa.gov
- ►Battery expiry date is current — replace or service before expiry
- ►Hydrostatic release inspected — releases at 3-10 meters depth
- ►Self-test performed and passed (brief self-test only — do not activate)
- ►Strobe light functional
- ►Mounted in bracket with clear water access for float-free deployment
- ►All pyrotechnic signals are within their stamped expiry date
- ►Minimum: 3 orange smoke, 3 red meteor, 3 red parachute for offshore day/night
- ►Stored in watertight container accessible from deck and from the life raft
- ►Crew briefed on operation of each type
- ►Electronic distress signals available as backup (strobe, LED)
- ►Expired flares disposed of safely — check local hazmat programs
- ►One Type I or offshore life jacket per person, plus one throwable Type IV
- ►Inflatable life jackets: CO2 cylinder unexpired, armed, bladder tested for airtightness
- ►Safety harnesses and tethers inspected: stitching, buckles, snap hooks
- ►Jacklines rigged before departure for offshore passages
- ►Tethers have at least one attachment point accessible while in the water
- ►Man-overboard light and drogue attached to each offshore life jacket
Navigation Systems Pre-Departure Check
GPS / Chartplotter
Verify latest chart update installed; test waypoint entry; test MOB button
Radar
Test sweep; verify range scale settings; test MARPA if installed; test guard zone
AIS Transponder
Verify MMSI programmed; check vessel data; confirm targets displaying correctly
Depth Sounder
Zero offset correct for transducer position; shallow alarm set; test alarm
Compass
Check deviation card for current year; compare to GPS heading at known heading
Navigation Lights
Test all circuits: steaming, running, stern, anchor; carry spare bulbs
Port Entry Planning: Customs, Immigration, and Clearance
Arriving in a foreign country without proper preparation can result in significant fines, vessel detention, and denial of entry. Port entry planning begins during the appraisal phase — not when the dock lines are being tossed.
Pre-Arrival Planning
- ►Research customs and immigration procedures for the destination port
- ►Confirm port of entry — entry must be made at an official port of entry, not a private anchorage
- ►Obtain cruising permit requirements in advance (Caribbean, Mexico, Bahamas each differ)
- ►Prepare crew and passenger manifest with passport numbers and nationalities
- ►Ensure all vessel documentation is current: USCG Certificate of Documentation or state registration
- ►Obtain ship's radio station license (required for HF radio in foreign waters)
- ►Confirm arrival during customs office hours — many ports charge overtime for after-hours clearance
Arrival Procedures
- ►Fly the Q flag (solid yellow) from the starboard spreader upon entering foreign waters
- ►Fly courtesy flag of the host nation below the starboard spreader
- ►Proceed directly to the designated port of entry — no stops, no anchoring, no shore contact
- ►Contact port authority or customs on VHF Ch 16 or designated channel
- ►All crew and passengers must remain aboard until clearance is granted
- ►Declare all required items: weapons, medications, alcohol quantities, food stuffs
- ►Pay all required fees and obtain clearance certificate (Zarpe or equivalent)
After Clearance
- ►Strike the Q flag once clearance is granted
- ►Keep all clearance documents aboard and available for inspection throughout the cruise
- ►Obtain cruising permit if required for the region
- ►Notify next port of entry of your planned arrival if required
- ►Maintain crew and passenger manifest accuracy — any changes require notification
- ►On departure, obtain clearance certificate (Despacho/Zarpe) for next destination
- ►Return to home country through a designated US Customs port of entry
Common Cruising Permit Requirements
- ►Bahamas: Cruising Permit required; pay upon arrival at designated port
- ►Mexico: Temporary Import Permit (TIP) for the vessel; obtain online or at port
- ►Eastern Caribbean: CARICOM Multilateral Air Services Agreement varies by island
- ►Canada: CBSA CANPASS program allows pre-clearance by phone for eligible vessels
- ►Firearms: most countries require declared firearms to remain aboard or in bond
Return to the United States
- ►Vessels must enter at a designated US Customs and Border Protection port of entry
- ►Report arrival immediately via CBP ROAM app, I-68 permit (Canada), or in person
- ►Crew must remain aboard until CBP clearance is granted (or app confirms)
- ►Declare all dutiable items, currency over $10,000, and restricted goods
- ►Bring all crew passports and vessel documentation to the CBP inspection
Emergency Planning for Offshore Passages
Emergency plans are written before the emergency happens. A crew that has not discussed MOB recovery, MEDEVAC procedures, or vessel flooding response will improvise under stress — and improvisation kills. Emergency planning is part of the IMO Plan phase.
Celestial navigation as a backup to GPS failure is covered in: Celestial Navigation for the USCG Exam.
- ►Assign a dedicated spotter immediately — never take eyes off the person in the water
- ►Throw a life ring, MOB pole, and any floating debris immediately
- ►Press MOB button on GPS/chartplotter to mark position
- ►Issue a MAYDAY on VHF Ch 16 with vessel name, MOB position, and description
- ►Use Quick Stop maneuver (jibe immediately and return to MOB position)
- ►At night: illuminate with searchlight; activate MOB light if victim wearing one
- ►Pre-assign recovery roles: helm, spotter, recovery crew with boarding ladder
- ►Assess patient: airway, breathing, circulation before calling for help
- ►Contact USCG on VHF Ch 16 for medical advice and evacuation coordination
- ►DAN (Divers Alert Network) and USCG provide free medical consultation at sea
- ►Identify the nearest port with medical facility — not just the nearest port
- ►Document all symptoms, vital signs, medications given, and time of onset
- ►Prepare landing zone for helicopter if MEDEVAC is ordered
- ►Brief crew on helicopter evacuation procedure before the passage
- ►Identify ports of refuge before departure — not when the weather hits
- ►For each leg, know the nearest port that provides shelter from the expected storm direction
- ►Confirm that the port of refuge is accessible at the expected tidal level and sea state
- ►File revised float plan with any change of destination
- ►Issue PAN PAN (urgency) before conditions reach MAYDAY level
- ►Deploy storm tactics before the crew is exhausted: heave to, sea anchor, run off
- ►Do not attempt inlet entry in breaking seas at night without local knowledge
- ►Issue MAYDAY immediately with position, nature of distress, and persons aboard
- ►Activate EPIRB manually — do not wait for the vessel to sink
- ►Begin dewatering: electric bilge pump, manual pump, and buckets simultaneously
- ►Locate and attempt to stop the source of flooding
- ►Prepare life raft for deployment: painter attached, CO2 not yet activated
- ►Don life jackets before the vessel becomes unstable
- ►Stay with the vessel as long as safe — it is easier to spot than people in the water
USCG Requirements for Offshore Operations
Federal regulations for offshore operations are drawn from multiple sources: 33 CFR for inland and coastal navigation, 46 CFR for vessel safety and inspection, and international conventions (SOLAS, STCW, MARPOL) for vessels in international service. The OUPV exam focuses on the requirements most applicable to small commercial vessels.
Safety Equipment
- ►Life jackets: one Type I (offshore) per person plus one throwable (Type IV)
- ►Visual distress signals: day and night pyrotechnics or approved electronic signals
- ►Navigation lights operational for day, night, and restricted visibility conditions
- ►Sound-producing device: whistle or horn
- ►Fire extinguishers: per vessel length requirements under 33 CFR Part 175
- ►Anchor with appropriate scope for water depth at the destination
- ►First aid kit appropriate for passage duration
Navigation and Communications
- ►VHF radio: required on inspected vessels; strongly recommended for all offshore passages
- ►Navigation charts: current, corrected charts for the entire route
- ►Compass: magnetic compass must be operable independent of electrical power
- ►GPS/chartplotter: satellite-based navigation; handheld backup recommended
- ►Radar: required on inspected vessels operating in reduced visibility
- ►EPIRB: required on uninspected commercial vessels; strongly recommended for all offshore
- ►Depth sounder: highly recommended for all offshore passages
Vessel Documentation
- ►USCG Certificate of Documentation or state certificate of number for US vessels
- ►Ship's radio station license required when operating HF/SSB radio in foreign waters
- ►Proof of insurance recommended (required by some foreign countries)
- ►USCG inspection certificate for inspected vessels (T-boat, passenger vessel)
- ►Stability letter if vessel operates under a stability requirement
- ►Load line certificate for vessels required to carry one
- ►International tonnage certificate for vessels over 24 meters operating internationally
Crew Qualifications
- ►OUPV (6-pack) license for carrying up to 6 passengers for hire on ocean and coastal routes
- ►100-ton Master license for vessels carrying more than 6 passengers or over 100 GRT
- ►STCW Basic Safety Training for all crew on inspected vessels in international service
- ►STCW endorsements as required by vessel type and trade
- ►Medical certificate (valid USCG physical) for credentialed officers
- ►Drug testing compliance for commercial mariners
- ►Crew documentation (Merchant Mariner Credential) for all licensed positions
USCG Exam Focus Areas: What You Must Know Cold
These are the highest-yield passage planning topics on the OUPV and Master exams. Every one of these points has appeared repeatedly on official USCG question banks.
The plan must be written — verbal passage plans are not plans
IMO Resolution A.893(21) requires a written passage plan. A discussion at the chart table is appraisal, not planning. The plan must document waypoints, courses, safety margins, abort points, watch schedules, and communications. On the exam: any answer saying the plan must be written is almost certainly correct.
Great circle routes appear curved on Mercator charts
This is the most counterintuitive chart fact. On a Mercator chart, a straight line is a rhumb line (constant course). A great circle (shortest distance) appears as a curve bowing toward the nearest pole. On a gnomonic chart, the reverse is true — great circles are straight lines. Know which chart shows which route as a straight line.
EPIRB registration is the captain's responsibility
A 406 MHz EPIRB must be registered with NOAA before the passage. An unregistered EPIRB still transmits a distress signal, but rescue coordination centers cannot identify the vessel and will waste time verifying it is not a false alarm. Registration is free, takes five minutes, and saves critical minutes during a real distress.
The Q flag is flown on starboard upon entering foreign waters
Before clearing customs, the Q flag (solid yellow) goes on the starboard spreader or starboard halyard. No shore contact until clearance is granted. This appears directly on the OUPV licensing exam. The wrong color, wrong side, or wrong timing are all tested wrong-answer traps.
Tide tables and current tables are different publications
A common exam trap: candidates confuse tide height with tidal current. The tide table gives water height above datum. The current table gives speed and direction of flow. High water and maximum flood current do not occur at the same time — there is a lag of 1-3 hours at most stations. Read the correct table for the information you need.
STCW: 10 hours rest minimum per 24-hour period
The STCW rest hour requirements apply to commercial vessel crew: minimum 10 hours of rest in any 24-hour period, with a maximum of 14 consecutive hours of work. This is not advisory — it is law on commercial vessels. On the exam, any watch schedule that gives less than 10 hours of rest in 24 hours violates STCW.
Practice Questions: Offshore Passage Planning
These questions follow the format of official USCG OUPV and Master examination questions. Work through each before reading the answer and explanation.
1.Which phase of the IMO passage planning model involves plotting waypoints and courses on the chart?
- A. Appraise
- B. Plan
- C. Execute
- D. Monitor
Explanation
The Plan phase translates the appraisal into a specific, documented passage plan including waypoints, courses, distances, safety margins, and contingency information. Appraisal gathers the information. Execute carries out the plan. Monitor compares actual position to the plan.
2.On a Mercator chart, a straight line between two points represents a:
- A. Great circle route
- B. Rhumb line
- C. Composite route
- D. Orthodrome
Explanation
A straight line on a Mercator chart is a rhumb line — a line of constant bearing that crosses all meridians at the same angle. A great circle appears as a curve on a Mercator chart. A gnomonic chart is the one where great circles appear as straight lines.
3.A vessel arriving in a foreign country before clearing customs must fly:
- A. The national ensign of the host country on the port spreader
- B. A solid yellow flag (Q flag) on the starboard side
- C. A solid red flag on the port side
- D. The yacht ensign on the stern
Explanation
The Q flag (quarantine flag — solid yellow) is flown on the starboard spreader or starboard halyard to signal the vessel has not yet cleared customs and is requesting pratique. No one may come aboard or go ashore until customs clearance is granted.
4.What is the minimum rest period required under STCW in any 24-hour period?
- A. 6 hours
- B. 8 hours
- C. 10 hours
- D. 12 hours
Explanation
STCW requires a minimum of 10 hours of rest in any 24-hour period. This rest may be divided into no more than two periods, one of which must be at least 6 hours. Additionally, the total rest over any 7-day period must be at least 77 hours.
5.The Rule of Twelfths is used to estimate:
- A. Fuel consumption at various engine speeds
- B. The tidal height change during each hour of the tidal cycle
- C. The distance to the horizon from a given height of eye
- D. The number of watches required for a given crew size
Explanation
The Rule of Twelfths approximates tidal height change as: 1/12 in the first hour, 2/12 in the second, 3/12 in the third, 3/12 in the fourth, 2/12 in the fifth, and 1/12 in the sixth. This means the tide rises and falls fastest in the middle two hours of the cycle.
6.When should an EPIRB be manually activated?
- A. Only when the vessel has sunk and the EPIRB floats free
- B. Immediately when a genuine life-threatening emergency exists and rescue assistance is needed
- C. Only after a MAYDAY on VHF Ch 16 has been transmitted and no response received
- D. Only when directed by the Coast Guard
Explanation
An EPIRB should be manually activated as soon as you determine that the situation is a genuine emergency requiring search and rescue assistance. Do not wait for the vessel to sink. Manual activation combined with a MAYDAY on VHF maximizes the speed of rescue response.
7.A passage plan identifies an abort point at waypoint 4. The purpose of this abort point is to:
- A. Mark the location where the vessel must anchor for the night
- B. Define a pre-determined position where a go/no-go decision will be made based on defined criteria
- C. Indicate the farthest point the vessel will travel from shore
- D. Mark the end of USCG radio coverage
Explanation
Abort points are pre-defined positions in the passage plan where the captain evaluates conditions against the passage's go/no-go criteria. If weather, mechanical condition, crew fatigue, or fuel consumption exceeds the defined limits at the abort point, the vessel diverts. The criteria must be defined before departure — not improvised when conditions deteriorate.
8.A tidal current table lists data for a reference station. You need the current at a secondary station 40 miles away. You should:
- A. Use the reference station time and speed without adjustment
- B. Apply the time difference and speed ratio corrections from the secondary station table
- C. Add 30 minutes to the reference station time as a standard correction
- D. Use the tide table instead of the current table for secondary stations
Explanation
Secondary stations require specific time difference and speed ratio corrections listed in the current tables. These corrections can vary by several hours and significant speed differences from the reference station. Using reference station data without correction at a secondary station is a common and potentially dangerous error.
Pro Tips from Experienced Offshore Captains
Textbook knowledge gets you the license. These hard-won lessons help you use it safely.
Start the passage plan two weeks before departure
Long-range weather models become useful about 10-14 days out. Starting the plan early lets you identify weather windows, research ports of entry, order charts that may need to be updated, and arrange crew visas or clearance documents that take time to obtain.
Never plan to arrive at a new inlet or anchorage after dark
Buoys are hard to see, depth can be misleading without local knowledge, and hazards that are obvious by day are invisible at night. Build your passage plan so that you arrive at unfamiliar ports before noon — this also leaves daylight for anchoring if your first choice is occupied.
The passage plan is written for the officer of the watch — not the captain
A well-written passage plan allows any qualified officer to stand a watch without waking the captain. It includes specific instructions: when to call the captain, what conditions require a course change, and what hazards to watch for. If the plan only makes sense to the person who wrote it, it is not a real plan.
Verify your EPIRB registration immediately before any offshore passage
NOAA registration data expires and ownership changes. Fifteen minutes on the NOAA beacon registration website before departure confirms that the EPIRB will alert rescuers to the right vessel with the right contact information. The battery and hydrostatic release expiry should be checked at the same time.
File a float plan with someone who will actually call the Coast Guard
A float plan filed with someone who will 'try to call you first' or 'wait a few more days' before alerting authorities defeats the purpose. Choose a contact who understands the instructions: if the vessel is more than X hours overdue, call USCG at this number with this information.
Plan for the worst-case fuel scenario, not the average
Fuel calculations should use the worst-case consumption rate — the rate measured in rough conditions with headwinds and adverse current, not the calm-day optimum. If you plan on 10 GPH and the passage delivers 14 GPH conditions, you are in serious trouble. Build in the margin.
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