Storm warning signals, sea anchor deployment, heaving to, broaching and pitch-poling, MOB recovery, Mayday procedures, EPIRB activation, and vessel stability concepts tested on the USCG OUPV and Masters license exams.
64 kts
Wind speed threshold for Hurricane Warning
7:1
Minimum scope ratio for storm anchoring
406 MHz
EPIRB transmission frequency to COSPAS-SARSAT
The National Weather Service issues four levels of marine warnings based on forecast wind speed. Visual display signals are flown at marinas, harbors, and Coast Guard stations. The USCG exam tests the knot thresholds and the visual signals for each level.
| Warning Level | Wind Speed | Daytime Signal | Nighttime Signal |
|---|---|---|---|
| Small Craft Advisory | 18 – 33 knots | One red pennant | Red light over white light |
| Gale Warning | 34 – 47 knots | Two red pennants | White light over red light |
| Storm Warning | 48 – 63 knots | One square red flag with black center | Two red lights |
| Hurricane / Tropical Storm | 64 knots or greater | Two square red flags with black centers | Red light over red light |
Exam tip: Tropical Storm Warning vs. Hurricane Warning
A Tropical Storm Warning covers sustained winds of 34 to 63 knots associated with a named tropical cyclone. A Hurricane Warning begins at 64 knots. Both use two square red flags by day and red-over-red lights at night. The distinction tested on the exam is the wind speed threshold, not the visual signal (they are the same).
A captain must interpret marine forecasts and recognize the early signs of deteriorating conditions before they become life-threatening.
Barometric Pressure Trend
A rapidly falling barometer — more than 0.06 inches (2 mb) per hour — indicates an approaching low pressure system and deteriorating conditions. A fall of 0.10 inches or more in three hours signals a gale or worse. A slow, steady fall over 12 to 24 hours suggests a weaker but broad system. A rising barometer after a low typically signals improving conditions but can bring strong northwesterly winds as the cold front passes.
Wind and Sea State Progression
Wind clocks (shifts clockwise) as a cold front approaches and veers further after passage. A veering wind that increases rapidly, combined with a falling barometer, signals an approaching front. Long swell from a distant direction often precedes local wind build by 12 to 24 hours. When swell and local wind waves combine from different directions, the resulting confused seas are more dangerous than either component alone.
VHF Weather Broadcasts
NOAA Weather Radio broadcasts continuous marine forecasts on WX-1 through WX-7. The coastal marine forecast includes winds, seas, visibility, and precipitation. Offshore forecasts extend to 200 nm. High Seas forecasts cover ocean basins. Listen for the gale watch, storm watch, and watch vs. warning distinction: a watch means conditions are possible; a warning means conditions are occurring or imminent.
Cloud Progression
The classic warm-front cloud progression from high to low: cirrus (feathery high clouds, 24 to 48 hours ahead) to cirrostratus (halo around sun or moon) to altostratus (milky overcast, rain within 12 hours) to nimbostratus (low, dark, steady rain). A cold front moves faster and brings a sharper wall of cumulonimbus clouds with squalls, strong gusty winds, and rapid wind shifts.
Rule of thumb: when in doubt, do not go out
The best time to make a go/no-go decision is before leaving the dock. Once offshore in deteriorating conditions, options narrow rapidly. Check the marine forecast from at least two sources before departure and monitor continuously underway. A small craft advisory for the afternoon can become a gale warning by evening if the system accelerates.
Preparation before storm conditions is far more effective than reactive measures in breaking seas. The USCG exam tests specific checklist items as well as the principle that reefing should be done early.
Deck Security
Bilges and Watertight Integrity
Fuel, Stability, and Systems
Safety Equipment
Navigation and Communication
When a vessel encounters conditions beyond what is comfortable or safe to continue passage, three primary tactics are available. The choice depends on sea room, vessel type, crew condition, and storm severity. The USCG exam tests all three tactics and the order in which a mariner should attempt them.
Heaving To
First choice in heavy weather — available to both sail and power vessels
Back the jib against the wind, lash helm to leeward; or on power, hold slow ahead into the seas at a comfortable angle
Vessel lies at a comfortable angle, crew can rest, forward motion nearly stops, windward slick helps smooth seas
Requires sea room to leeward; may not work in very steep beam seas; some hull forms do not heave to well
Running Before the Sea
Used when sea room exists to leeward and the vessel must make progress or avoid a lee shore
Run dead downwind or at a slight angle; tow warps or a drogue from the stern to reduce speed and prevent broaching
Reduces apparent wind and wave impact; allows progress toward shelter; familiar handling for most mariners
Broaching, pitch-poling, and pooping (following sea washing over the stern) are primary dangers; requires constant active steering
Lying Ahull
Last resort when crew is exhausted or unable to maintain active management
All sail down, helm lashed to leeward, no power; vessel finds its own attitude to the seas passively
Requires no crew effort
Beam-on position is most vulnerable to knockdown and capsize; only appropriate in survivable conditions with no sea room concerns
A sea anchor (also called a parachute anchor) is deployed from the bow to hold the vessel head-to-sea. A drogue is deployed from the stern to slow the vessel while running before the sea. The USCG exam tests the difference in deployment direction, the purpose of each, and the role of the tripping line.
Sea Anchor (Parachute) — Bow Deployment
Preparation
Flake the rode on deck in a figure-eight pattern to prevent fouling. Attach the tripping line to the apex of the sea anchor — the tripping line must be long enough to reach from the sea anchor at its operational depth back to the vessel.
Rode Length
Veer 300 to 600 feet of nylon rode — or five to ten times the vessel length. The goal is to position the sea anchor in the wave trough ahead of the vessel while the vessel is on the back of a wave. This phase relationship prevents the vessel and anchor from riding the same wave face, which would reduce effectiveness.
Snubber
Attach a nylon snubber between the rode and the bow cleat. The snubber stretches under load, absorbing shock that would otherwise transmit directly to the cleat and deck hardware. Heavy nylon rode provides its own shock absorption but a snubber is still advisable on chain-to-nylon transitions.
Tripping Line
The tripping line, attached to the apex (closed end) of the parachute, allows recovery without bringing the vessel alongside the sea anchor under tension. When ready to recover, haul on the tripping line: this collapses the parachute by pulling the apex toward the bow, spilling water and reducing drag to near zero.
Effect
The sea anchor reduces drift from three to five knots to less than one knot, keeps the bow into the seas, and allows the crew to rest. The rode stretches and relaxes with each wave, avoiding shock loads. Monitor scope continuously — additional rode may be needed as seas build.
Drogue — Stern Deployment
A drogue is a smaller drag device deployed from the stern while running before the sea. Its purpose is to slow the vessel to a speed where it does not surf uncontrollably down wave faces, reducing the risk of broaching and pitch-poling. Heavy warps (large-diameter dock lines or anchor rodes) streamed in a bight from both stern cleats serve the same function as a purpose-built drogue and are frequently the only gear available on short-handed vessels.
Warp Method
Veer 200 to 400 feet of heavy line in a bight (loop) from both stern quarters. The bight drags in the water, creating resistance. Multiple lines or a loop reduces the risk of a single line parting. Nylon absorbs shock better than polypropylene or Dacron.
Dedicated Drogue
A series drogue (Jordan series drogue) consists of hundreds of small cones on a long bridle. The distributed drag is very steady and highly effective. It is attached to both stern quarters by a bridle and veered on 200 feet or more of rode. A dedicated drogue provides more controllable resistance than warps.
Running before steep following seas is the most dangerous point of sail in heavy weather. Two catastrophic failure modes — broaching and pitch-poling — are the primary exam topics. The USCG exam tests both definitions and the prevention techniques for each.
Broaching
A sudden, violent, uncontrolled yaw that brings the vessel broadside to the seas. The vessel is picked up by a wave, the stern is accelerated faster than the bow, and the rudder loses effectiveness as the vessel surfs. The bow buries and the vessel spins 90 degrees or more. Once broadside to a breaking sea, knockdown or capsize is likely.
Prevention:
Pitch-Poling
An end-over-end capsize in which the bow is driven underwater and the stern is thrown over it. Occurs when a vessel surfs at high speed into the trough ahead and the bow buries in the back of the preceding wave. More likely in short, steep, breaking seas and in vessels with fine, low-buoyancy bows.
Prevention:
Surf Riding
Surf riding (or surfing) occurs when a vessel is lifted by a wave and accelerates down its face. Controlled surfing can be manageable in gentle swells but in steep breaking seas the vessel can exceed its hull speed dramatically, making steering unresponsive. The critical lesson: if the vessel is surfing, she is too fast. Stream warps or a drogue immediately. The exam differentiates between the controlled state of surf riding and the uncontrolled end state of broaching.
Vessel stability — the tendency to return to an upright position after being heeled — can be degraded by multiple factors that accumulate in heavy weather. The USCG exam tests the specific mechanisms by which each factor reduces the righting moment.
Free Surface Effect
When a partially filled tank rolls with the vessel, the liquid shifts to the low side, moving the center of gravity (G) outboard and effectively raising it. This reduces the metacentric height (GM) and therefore reduces the righting arm (GZ) at all angles of heel. The effect is calculated by the free surface moment: (length of tank) times (beam of tank cubed) divided by 12, multiplied by liquid density, divided by displacement. For the exam: free surface reduces GM; tanks should be full or empty to eliminate it; the effect is the same at 10 percent and 90 percent full.
Shifted Cargo
When deck or hold cargo shifts to one side, G moves off centerline in the direction of the shift and may also rise if the cargo was low. The vessel develops a permanent list toward the shifted cargo. The righting arm on the low side is reduced; on the high side it is increased. A vessel with a severe list from shifted cargo may have inadequate righting arm to resist a breaking sea from the low side and capsize. The exam tests that the correction for cargo-induced list is to restow the cargo to its original position, not to move passengers or ballast fuel.
Topside Water and Waterlogged Conditions
Green water shipped on deck and retained by closed deck drains or damaged freeing ports adds significant weight high on the vessel. A wave that strikes the deck and pools adds weight at deck level — far above the center of gravity — immediately reducing GM. Deck drains and freeing ports must be kept clear in heavy weather. A vessel that has shipped water into the cockpit, cabin, or bilge has reduced freeboard and compromised stability simultaneously. Each foot of freeboard lost increases the vulnerability to the next wave.
Flooding and Progressive Flooding
Flooding below decks initially adds weight at a low point, which may temporarily improve initial stability by lowering G. However, free surface in the flooded compartment immediately begins reducing GM. As flooding progresses, displacement increases, the vessel sinks, freeboard is lost, and subsequent waves more easily overtop the deck. Asymmetric flooding (one side more flooded than the other) creates a list. If flooding cannot be controlled, all efforts must shift to abandoning ship in a controlled manner rather than uncontrolled sinking. The exam tests: (1) flooding reduces freeboard; (2) free surface in flooded compartments reduces GM; (3) asymmetric flooding causes list corrected by counter-flooding or pumping.
MOB in heavy weather is among the most dangerous maritime emergencies. Wave heights, vessel motion, and cold water reduce survival time dramatically. Every second without a dedicated spotter reduces the probability of rescue. The USCG exam tests the Williamson Turn and the approach angle.
Immediate Actions (first 60 seconds)
Return Maneuvers
Williamson Turn (heavy weather / restricted visibility)
Put the helm hard over to the same side as the MOB. When 60 degrees off the original course, shift the helm to the opposite side. Continue turning to a reciprocal heading (180 degrees from original). This returns the vessel down its exact track. Best in heavy weather because it returns to the track even after a delay.
Quick Stop (calm or light conditions)
Immediately turn toward the MOB side, gybe or tack if under sail, and maneuver to return. Keeps the vessel close to the MOB but requires continuous visual contact.
Approach and Recovery
Approach the victim from downwind and downsea so the vessel drifts toward the victim rather than over them. Stop all way before the victim reaches the hull. In heavy weather, the vessel motion is violent — a rigid boarding ladder on a pitching hull can injure a victim. Use a lifting sling, a swim platform, or a halyard-and-bosun-chair for retrieval if the victim cannot climb. A hypothermic victim may be unable to assist in their own recovery. Have two crew ready at the point of recovery; in heavy weather, the rescuer can become a second victim.
When a vessel is in grave and imminent danger, the two primary distress tools are the Mayday call on VHF Channel 16 and EPIRB activation. The USCG exam tests the exact format of the Mayday call, the EPIRB frequencies, and the two EPIRB categories.
Mayday Call Format — VHF Channel 16
MAYDAY, MAYDAY, MAYDAY
THIS IS [vessel name, spoken three times]
MAYDAY [vessel name]
MY POSITION IS [latitude and longitude, or bearing and distance from known point]
Nature of distress: [sinking, fire, medical emergency, flooding, dismasted, etc.]
Number of persons on board: [state the number]
Any other pertinent information: [vessel description, color, EPIRB activated, abandoning ship, etc.]
OVER
Wait 1 minute for a response after each transmission. If no response, repeat. If possible, also transmit on DSC (Channel 70 digital) before the voice Mayday — the DSC alert sends your MMSI number and GPS position automatically to all vessels and shore stations with DSC capability.
EPIRB Categories
Category I (Float-Free)
Mounted in a hydrostatic release bracket. When submerged in 1 to 4 meters of water, the hydrostatic release activates, freeing the EPIRB. It floats to the surface and activates automatically. Best protection for crew who cannot manually activate before abandoning. The hydrostatic release must be replaced every two years or per the manufacturer schedule.
Category II (Manual)
Must be manually activated. Not designed for float-free deployment. Less expensive but requires crew action. Suitable for inland and nearshore vessels where manual activation is practical before abandoning.
EPIRB Technical Facts
The decision to seek a port of refuge versus riding out weather offshore requires rapid assessment of multiple variables. Making the wrong call — particularly approaching a bar entrance in breaking seas — can be more dangerous than remaining offshore in the storm.
Decision Factors
Remain Offshore If
Seek Refuge If
Storm Anchoring Techniques
Deploy 7:1 or greater scope; nylon rode stretches to absorb shock; all-chain creates catenary shock absorption through weight; calculate scope on maximum expected depth including tidal range
Two anchors on the same rode in series; the primary anchor is set first, then the second anchor is dropped on a short chain leader between the two; adds holding power but does not provide redundancy if the rode parts
Two separate rodes set at 30 to 60 degrees apart from the bow; distributes load; prevents the vessel from sailing in circles at anchor; best for locations with restricted swinging room
A heavy weight (30 to 50 lbs) dropped down the rode to depress the angle of pull and increase catenary; reduces shock loads and the chance of the anchor breaking out in surging conditions
Federal law (33 CFR Part 175) requires approved visual distress signals (VDS) on most recreational vessels operating on coastal and offshore waters. Heavy weather conditions are precisely when VDS must be readily accessible — not buried under gear in a locker. The USCG exam tests the number required, approved types, and proper use.
| Signal Type | Day / Night | Approved Substitute | Key Points |
|---|---|---|---|
| Parachute rocket flare | Night (and day) | None | Reaches 1,000 ft altitude; visible 5+ miles; most effective single signal; fire slightly downwind |
| Handheld red flare | Night (and day) | None | Burns 1 to 3 minutes; must hold away from body; three required |
| Orange smoke signal | Day only | None | Highly visible in daylight; wind disperses smoke; less effective in rain or heavy spray |
| Orange distress flag (3x3 ft) | Day only | None | Wave or attach to highest point; non-pyrotechnic; no expiration |
| Electric SOS light | Night only | Replaces night flares | Flashes SOS automatically; rechargeable; no expiration; USCG approved substitute for three night signals |
| Signal mirror | Day only | Supplement only | Can signal aircraft or vessels; effective range 10+ miles in sunlight; inexpensive and reliable |
Requirements for Coastal Waters
Vessels on coastal waters used at night must carry three day-use signals and three night-use signals. Vessels used only during the day must carry three day-use signals. Pyrotechnic signals must bear a USCG approval number and must not be past their expiration date. Expired signals may be retained as backup but do not count toward the required three. Vessels under 16 feet on inland waters used during the day are exempt from VDS requirements.
How to Fire a Parachute Flare
Point the launcher slightly downwind and upward at approximately 60 degrees — not straight overhead. Firing into the wind causes the flare to come straight down; directly overhead wastes the parachute descent time over the vessel. The flare should drift over or slightly past the vessel on the downwind side, burning at altitude for maximum visibility. In very low cloud cover, fire at a lower angle so the flare burns below the cloud base where it can be seen by SAR aircraft and vessels.
Effective watchkeeping is the first line of defense in heavy weather. The watch officer must monitor weather, vessel systems, crew condition, and traffic simultaneously. Communication discipline — maintaining Channel 16 watch, broadcasting intentions, and monitoring weather updates — can prevent distress situations before they develop.
Continuous Channel 16 Watch
VHF Channel 16 is the international distress, safety, and calling frequency. All vessels underway are required to maintain a watch on Channel 16 (or Channel 9 for recreational vessels). In deteriorating conditions, the watch officer must monitor Channel 16 continuously. Distress calls from nearby vessels, USCG broadcasts of storm warnings (Marine Safety Broadcasts), and Pan-Pan urgency messages are all transmitted on Channel 16. Modern VHF radios with dual-watch capability allow monitoring Channel 16 simultaneously with a working channel.
SECURITE and Marine Safety Broadcasts
The USCG broadcasts Marine Safety Information (MSI) on VHF Channel 16 and WX channels at scheduled intervals. A SECURITE call (pronounced say-cure-ee-TAY) precedes a navigation safety announcement — such as a new storm warning, hazard to navigation, or special notice to mariners. When you hear SECURITE SECURITE SECURITE on Channel 16, shift to the indicated working channel and listen. These broadcasts may contain weather upgrades (gale to storm, storm to hurricane) that were not forecast when you departed.
Float Plan and Check-In Schedule
Before any offshore passage in conditions that could deteriorate, file a detailed float plan with a responsible person ashore. The float plan must include: vessel description and MMSI number, complete crew list with contact information, departure point, route, intended ports of call, and expected arrival time. Establish a check-in schedule — a specific time at which you will contact the float plan holder by phone or radio. If the vessel misses a check-in, the float plan holder initiates contact with the USCG. Most offshore SAR operations begin because a float plan was activated — the absence of a float plan delays rescue by hours.
Pan-Pan vs. Mayday
Pan-Pan (pronounced PAHN PAHN) is the urgency signal — one level below Mayday. Use Pan-Pan when the vessel or a person on board is in urgent situation that does not yet require immediate assistance. Examples: vessel with engine failure drifting toward a lee shore, injured crew member requiring medical advice, vessel taking on water but still manageable. The Pan-Pan call follows the same format as Mayday but opens with PAN-PAN PAN-PAN PAN-PAN. If the situation deteriorates to grave and imminent danger, upgrade to Mayday. The USCG exam tests the distinction: Pan-Pan for urgent but not immediately life-threatening; Mayday for grave and imminent danger of loss of life or vessel.
Immersion in cold water is a life-threatening emergency. In water below 50 degrees Fahrenheit, an unprotected person may lose the ability to swim within minutes and lose consciousness within 30 minutes. The USCG exam tests cold water survival times, the HELP position, and the role of immersion suits.
Below 32 F
Under 15 min
Expected survival time without immersion suit
32 to 40 F
15 to 30 min
Estimated time to unconsciousness
50 to 60 F
1 to 6 hrs
Survivable with PFD and HELP position
HELP Position
HELP stands for Heat Escape Lessening Position. In the water, draw the knees to the chest and cross the arms over the chest to protect the groin, armpits, and neck — the areas of greatest heat loss. A PFD must be worn to maintain the HELP position without active swimming. HELP can extend survival time by 50 percent or more compared to treading water, which accelerates heat loss. If multiple survivors are in the water together, the HUDDLE position — facing inward with arms and legs interlinked — combines the heat conservation of HELP with shared body warmth.
Immersion Suits
Immersion suits (also called survival suits or gumby suits) are required on commercial vessels operating in cold water and are strongly recommended for offshore recreational passages north of 35 degrees latitude. A properly donned immersion suit insulates the entire body and provides buoyancy. Survival time in a suit in 40 F water extends from under 30 minutes to several hours. The USCG exam tests that immersion suits must be donned in under 2 minutes, must be accessible without entering the machinery space, and must bear USCG approval. Practice donning the suit before departure — most people cannot complete it correctly under pressure without practice.
The most frequently tested heavy weather concepts on the USCG OUPV and Masters exams. Memorize these before test day.
| Topic | Key Fact | Common Wrong Answer |
|---|---|---|
| Small Craft Advisory threshold | 18 to 33 knots | 25 knots or 15 knots — exact thresholds vary by question phrasing |
| Gale Warning threshold | 34 to 47 knots | 30 knots or 50 knots |
| Storm Warning threshold | 48 to 63 knots | Confused with gale (34–47) — memorize by groups |
| Hurricane Warning threshold | 64 knots or greater | 60 knots — must be 64 |
| EPIRB primary frequency | 406 MHz (satellite) | 121.5 MHz — that is the homing frequency, not the primary |
| EPIRB homing frequency | 121.5 MHz | 406 MHz — reversal is the most common error |
| Mayday channel | VHF Channel 16 | Channel 22A — that is USCG working channel, not distress |
| Williamson Turn when to shift helm | 60 degrees off original course | 90 degrees or after a full minute |
| Free surface effect on stability | Reduces GM (righting moment) | Increases stability — common reversal |
| Sea anchor rode length | 5 to 10 times vessel length | Equal to vessel length — far too short |
| Tripping line purpose | Collapses sea anchor for recovery | Stops the sea anchor from diving |
| First choice heavy weather tactic | Heave to | Lying ahull — that is last resort |
| Broaching prevention | Tow warps from stern | Increase speed — the opposite of correct |
| Storm scope ratio | 7:1 minimum | 5:1 — that is normal conditions minimum |
| Category I EPIRB | Float-free, automatic activation | Must be manually activated — that is Category II |
Abandoning ship is the option of last resort. A vessel — even a disabled, flooded vessel — is almost always a safer platform than a life raft in heavy weather. The decision to abandon ship must be deliberate: when the vessel is clearly sinking or on fire beyond control, not simply because conditions are severe. The USCG exam tests abandon ship priorities and life raft procedures.
Abandon Ship Priority Sequence
Send Mayday
Transmit Mayday on VHF Channel 16 and activate DSC distress. State position, nature of distress, number of persons on board, and vessel description. Give SAR assets maximum time to respond before you leave the vessel.
Activate EPIRB
Activate the EPIRB manually even if it is set to automatic — confirm it is transmitting. If possible, take the EPIRB into the life raft. A transmitting EPIRB inside the raft dramatically improves homing accuracy for SAR aircraft.
Don Immersion Suits and PFDs
All crew members don immersion suits or PFDs before entering the water. Cold water incapacitates quickly — immersion suits extend survival time dramatically. Do not wait until the vessel is sinking to don them.
Prepare Life Raft
Move the life raft to the leeward side of the vessel. Do not inflate it on a vessel that may sink and pull it under. Tie the painter to a strong point, then deploy the raft. If hydrostatic release is fitted, confirm the weak link will part if the vessel sinks.
Gather Survival Gear
If time permits: grab the ditch bag (EPIRB, flares, water, food, first aid, handheld VHF, signal mirror, knife), fresh water containers, and any additional flotation. Do not delay abandonment waiting for gear — survival is the priority.
Board Without Entering Water
Board the life raft from the vessel without entering the water if at all possible. Cold water shock from immersion is a significant cause of death even before hypothermia. Use a boarding ladder or swing directly into the raft.
Stay Near the Vessel
Remain near the vessel until it sinks or is clearly dangerous (fire, explosion risk). A vessel is easier to find by SAR than a life raft. If the vessel remains afloat, board it again. The general rule: step up into the raft — never step down into the water.
Life Raft Survival Priorities
Once in the life raft, immediate priorities in order:
Ditch Bag Contents
A prepared ditch bag contains items not included in the life raft survival pack:
These questions cover the topics most frequently tested on the USCG OUPV and Masters examinations for heavy weather seamanship.
Nail the Test includes USCG-format practice questions on storm warnings, sea anchors, heavy weather tactics, stability, and distress procedures — with explanations for every answer.
Start Free PracticeNo account required to start. OUPV and Masters exam coverage.
These terms appear directly in USCG exam questions. Know each definition precisely.
Broaching
Sudden, uncontrolled yaw bringing a vessel broadside to following seas; primary danger of running before breaking waves
Pitch-poling
End-over-end capsize caused by the bow burying and the stern flipping over; most likely in steep breaking seas at surfing speeds
Heaving to
Balancing sail and rudder forces to bring a vessel to near standstill at a comfortable angle to wind and seas; first choice heavy weather tactic
Lying ahull
Passive storm tactic with all sail furled and helm lashed; beam-on to seas; last resort only
Sea anchor
Parachute or cone deployed from the bow to hold the vessel head-to-sea and reduce drift; deployed on 5 to 10 times vessel length of nylon rode
Drogue
Drag device deployed from the stern while running before the sea; slows the vessel and reduces risk of broaching
Tripping line
Line attached to the apex of a sea anchor to collapse it for recovery; essential for safe retrieval without powering up to the anchor
Free surface effect
Reduction of GM caused by liquid sloshing in a partially filled tank; reduces righting arm; eliminated by filling or emptying tanks completely
Pooping
A following sea breaking over the stern; can flood cockpit or cabin; prevented by reducing speed and using a drogue
Swamping
Flooding from above — waves breaking into the vessel — as distinct from flooding through hull penetrations
Lee shore
A shore toward which the wind is blowing; approaching a lee shore in heavy weather with engine failure is one of the most dangerous situations in coastal seamanship
Knockdown
A sudden heeling of the vessel to 90 degrees or beyond caused by a breaking sea; a full knockdown may immerse the mast; recovery depends on sufficient righting energy (GZ area)
Capsize
The vessel heels past its angle of vanishing stability and cannot return upright; the probability of capsize increases dramatically once the vessel is beam-on to breaking seas
Catenary
The downward curve in an anchor rode or tow line caused by the weight of chain; acts as a shock absorber by changing shape before transmitting load to the cleat or windlass
Sentinel (Kellet)
A weight dropped down the anchor rode to deepen catenary and reduce peak loads; typically 30 to 50 lbs; improves holding in surge or storm conditions
DSC (Digital Selective Calling)
Digital VHF protocol on Channel 70 that transmits a distress alert including MMSI number and GPS position to all DSC-equipped vessels and shore stations automatically
MMSI (Maritime Mobile Service Identity)
9-digit number assigned to a vessel for DSC radio communications and AIS; must be registered with the FCC or a delegated authority; included in EPIRB registration
Hydrostatic release
Device that automatically releases an EPIRB or life raft from its mounting bracket when submerged 1 to 4 meters; Category I EPIRBs and most coastal life rafts use hydrostatic releases
Anchoring Guide
Scope calculations, anchor types, dragging signs
Vessel Stability
GM, righting arm, stability curves
Voyage Planning
Float plans, weather routing, route selection
VHF Radio
Channel 16, DSC, Mayday protocol
Rules of the Road
ColRegs, lights, shapes, sound signals
Captain License Prep
Full exam coverage for OUPV and Masters