Nautical terms
34 of 469 terms in Safety & emergencies. Show all
B
- Backfire flame arrestor (Flame arrestor, Flame arrester, BFA) Safety & emergencies
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A device on the air intake of an inboard gasoline engine that stops flame from a backfire escaping into the engine space. Gasoline inboards (not outboards) must have an approved one, secured with a flame-tight connection.
- Blower (Bilge blower, Engine room blower, Powered ventilation) Safety & emergencies
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An exhaust fan that pulls fuel vapors out of an engine or fuel-tank compartment. Gasoline-powered boats need ventilation, and many have a label saying to run the blower at least 4 minutes and sniff the bilge for fumes before starting.
After fueling the Coast Guard advises opening hatches, running the blower at least four minutes and checking by smell for gasoline vapors before starting.
C
- Capacity plate (Maximum capacity plate) Safety & emergencies
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A label on many smaller boats showing the maximum number of people and weight the boat can safely carry. Do not exceed it; load evenly and keep weight low.
If there is no plate, the Coast Guard suggests asking the builder or a naval architect; its rule of thumb (length times width divided by 15, for 150-pound people) does not account for boat volume.
- Carbon monoxide (CO, CO poisoning) Safety & emergencies
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A colorless, odorless poisonous gas in engine and generator exhaust. It can build up in cabins and around the swim platform and rear deck, and it injures or kills boaters every year.
The Coast Guard advises keeping people off the swim platform and away from the rear deck while engines or the generator run, and keeping engines well maintained.
- Channel 16 (VHF channel 16, 156.800 MHz) Safety & emergencies
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The international VHF-FM distress, safety and calling channel. Boats with a VHF radio switched on should monitor 16 (or channel 9, the recreational calling channel) when not talking; after first contact, move to a working channel.
The Coast Guard asks boaters not to use channel 16 for radio checks or general chat.
- Cold water immersion (Cold shock, Cold incapacitation) Safety & emergencies
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What happens in the first minutes after falling into cold water: an uncontrolled gasp and rapid breathing (cold shock) that can cause drowning, then, within about 10 minutes, loss of useful movement in hands, arms and legs, well before hypothermia sets in.
This is a key reason to wear a life jacket rather than just carry one.
D
- Distress flag (Orange distress flag) Safety & emergencies
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An orange flag at least 3 by 3 feet with a black square and a black ball, marked as meeting Coast Guard requirements. It counts as a day-only visual distress signal and is most visible waved on a boat hook or flown from a mast.
E
- Electronic visual distress signal device (eVDSD, Electric distress light, Distress light) Safety & emergencies
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A battery-powered light that automatically flashes SOS and is certified to Coast Guard or RTCM standards. It meets the night-time visual distress signal requirement without the fire risk of flares.
A plain high-intensity white strobe is recognized as a distress signal on inland waters, but it does not satisfy the carriage requirement.
- Engine cut-off switch (ECOS, Kill switch, Engine cut-off switch link, Lanyard) Safety & emergencies
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A switch, usually with a lanyard clipped to the operator, that stops the engine if the operator is thrown from the helm. On boats under 26 feet that have one, federal law requires the operator to use it when running on plane or above displacement speed.
- EPIRB (Emergency Position Indicating Radio Beacon, 406 MHz EPIRB) Safety & emergencies
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A marine distress beacon that sends a coded 406 MHz signal via satellite to rescue authorities, often with a GPS position, plus a homing signal and strobe. Category I units float free and switch on automatically if the boat sinks; Category II are manual.
US-coded 406 MHz beacons must be registered with NOAA (free) and the registration renewed every two years. Mount a Category I unit outside the cabin where it can float free.
F
- Fire extinguisher (Portable fire extinguisher) Safety & emergencies
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Boats with closed living spaces, closed compartments where fuel or flammables are stored, unsealed double bottoms or permanent fuel tanks must carry Coast Guard-approved, marine-type hand-portable extinguishers: 5-B or 20-B for boats built 2018 and later. The number required depends on length.
Boats of model year 2017 or older may keep B-I or B-II extinguishers until they are no longer serviceable. Non-rechargeable units expire 12 years from the date stamped on the bottom.
- Fire extinguisher ratings (Class A fire, Class B fire, Class C fire, 5-B, 20-B) Safety & emergencies
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The letter shows the kind of fire an extinguisher is for: A for ordinary combustibles (wood, paper, trash), B for flammable liquids like fuel, oil and grease, C for energized electrical equipment. The number shows how much agent it holds; a higher number is bigger.
Boats must carry Class B marine-type extinguishers; a multipurpose "A:B:C" unit is fine if its B rating and Coast Guard approval meet your boat's requirement.
- Fixed fire extinguishing system (Engine room fire system, Automatic fire extinguisher) Safety & emergencies
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A Coast Guard-approved extinguishing system permanently installed to protect the engine compartment. Having one reduces the number of portable extinguishers the boat must carry.
- Flare (Pyrotechnic distress signal, Aerial flare, Hand-held flare) Safety & emergencies
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A pyrotechnic visual distress signal: hand-held or aerial red flares (day and night), parachute flares and red meteors, or orange smoke (day only). If you rely on pyrotechnics you need at least three for day and three for night; some combination flares count for both.
Pyrotechnics expire 42 months after manufacture; expired ones may be kept as extras but do not count. Store them cool and dry, and handle aerial launchers with care.
- Float plan Safety & emergencies
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A written note, left with a responsible person ashore, of who is aboard, a description and photo of the boat, where you are going and when you expect to be back, so they know when and where to have a search started.
H
- HELP position (Heat Escape Lessening Posture, H.E.L.P.) Safety & emergencies
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Heat Escape Lessening Posture: in cold water with a life jacket on, draw your knees to your chest and hug your arms across it to protect the areas that lose the most heat. Groups in the water should huddle together.
- Hypothermia Safety & emergencies
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A dangerous drop in the body's core temperature from exposure to cold water, air or wind. How fast it sets in depends mostly on water temperature, and to a lesser extent on body size, clothing and behavior.
To slow heat loss, keep your life jacket on, get as much of your body out of the water as you can (onto a capsized hull if possible), and use the HELP posture or a group huddle.
Sources disagree on shortest time to exhaustion or unconsciousness in cold water — left out rather than guessed. Check your local authority.
uscgboating.org · icdept.cgaux.org · nauticalcharts.noaa.gov
I
- Immersion suit (Survival suit) Safety & emergencies
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An insulated, buoyant suit covering the whole body that delays hypothermia in cold water. The Coast Guard suggests one for each person on boats operating offshore in cold waters.
- Inflatable life jacket (Inflatable PFD) Safety & emergencies
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A compact life jacket that fills from a gas cylinder, in many models automatically when it hits the water. It only counts toward the carriage requirement if the cylinder is full and all status indicators are green; many are approved only when worn.
The Coast Guard says inflatables are adult sizes only and not appropriate for weak or non-swimmers; service them per the maker's instructions.
J
- Jackline (Jack line) Safety & emergencies
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A strong line or strap run along the deck from bow to stern that a crew member's safety harness tether clips onto, so they can move about the deck without being swept overboard.
L
- Life raft (Liferaft) Safety & emergencies
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An inflatable survival craft stowed in a canister or valise, big enough for everyone aboard, with an emergency equipment pack. The Coast Guard suggests one for boats going offshore or far from rescue, serviced as the maker specifies.
M
- Man overboard (MOB, Crew overboard, Person overboard) Safety & emergencies
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The shout that someone has fallen off the boat, and the emergency of getting them back. Shout it with the side ("Man overboard, port side!") so everyone knows where to look.
The Williamson turn is one maneuver used to bring a powered vessel back along its own track to the person.
- Mayday (Distress call) Safety & emergencies
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The spoken radio distress signal, repeated three times, meaning grave and immediate danger to life or the boat; it has priority over all other calls. Call on VHF channel 16 with the boat's name, position, nature of distress, number aboard and help needed.
A DSC-equipped VHF with an MMSI and GPS connection can send a distress alert with your position by holding the red button for about 5 seconds.
P
- Pan-pan (Urgency call) Safety & emergencies
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The spoken radio urgency signal, said three times, for an urgent message about the safety of a person or boat when there is not yet an immediate threat to life.
It has priority over safety calls but not over a Mayday; a pan-pan situation can grow into a Mayday.
- Performance level (Level 50, Level 70, Level 100, Level 150, Level 275) Safety & emergencies
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The newer life jacket rating: the number is the minimum buoyancy in newtons. Level 50 and 70 are for use near shore with help close by; Level 100 for sheltered water; Level 150 turns an unconscious wearer face up for general use; Level 275 is for offshore in extreme conditions.
A higher level means more flotation and better turning, suited to longer waits for rescue; the Coast Guard notes the best life jacket is the one you will actually wear.
- Personal flotation device (PFD, Life jacket, Lifejacket, Wearable PFD) Safety & emergencies
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The Coast Guard's term for life jackets and buoyancy aids. Every recreational boat must carry a Coast Guard-approved wearable PFD of the right size for each person aboard, readily accessible, and in good and serviceable condition.
Children under 13 must wear one while the boat is underway unless below deck or in an enclosed cabin (federal rule; some states differ). Drowning is the leading cause of boating deaths.
- PFD type (Type I PFD, Type II PFD, Type III PFD, Type V PFD) Safety & emergencies
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The older way of rating life jackets, still on many labels: Type I turns most unconscious wearers face up and has the most buoyancy; Type II turns some; Type III supports a conscious person upright; Type V is approved only for specific uses stated on the label; Type IV is a throwable.
Federal regulations now speak of "wearable" and "throwable" PFDs, and newer jackets carry performance levels instead of types. The Coast Guard guide lists both so you can compare labels.
- PLB (Personal Locator Beacon) Safety & emergencies
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A pocket-sized 406 MHz distress beacon carried by a person, activated by hand only. Like an EPIRB it alerts rescuers by satellite, and many include GPS; its battery runs at least 24 hours once on.
Register it with NOAA like an EPIRB.
S
- Securite (Securité, Safety call) Safety & emergencies
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The spoken radio safety signal, said three times, before an important safety message for other mariners. It ranks below Mayday and Pan-pan but ahead of routine calls.
- Sound-producing device (Horn, Whistle, Ship's bell) Safety & emergencies
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Vessels 12 m (39.4 ft) and longer must carry a whistle (horn), and those 20 m (65.6 ft) and longer also a bell. Smaller boats must have some other means of making an efficient sound signal.
T
- Throwable device (Type IV PFD, Throwable PFD, Throw cushion, Ring buoy) Safety & emergencies
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A cushion or ring buoy meant to be thrown to someone in the water, not worn. Boats 16 feet and longer (except canoes and kayaks) must carry one, kept immediately available.
V
- Vessel Safety Check (VSC, Courtesy safety check) Safety & emergencies
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A free check of your boat's required safety equipment offered by volunteer examiners from the Coast Guard Auxiliary and America's Boating Club (US Power Squadrons), who also explain the rules and answer questions.
- Visual distress signals (VDS) Safety & emergencies
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Coast Guard-approved flares, smoke, distress flags or electric lights that boats must carry on coastal waters, the Great Lakes and connected waters more than 2 nautical miles wide. Most boats need signals for both day and night use.
Boats under 16 feet, open sailboats under 26 feet without an engine, manually propelled boats and boats in organized events need only night signals when out between sunset and sunrise.
W
- Williamson turn Safety & emergencies
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A maneuver that brings a vessel under power back onto its own track in the opposite direction, used to return to a person who fell overboard when you are not sure exactly where they are.
General guidance for recreational boaters, researched from the sources listed and written in our own words. Your equipment manuals, local knowledge, the Navigation Rules and a qualified instructor come first.