SERVICE AREA
Boating Glossary
A working vocabulary for boat owners: Defined the way they're used on the water, not the way they appear in a manual.
This glossary collects the terms that come up most often in our work with boat owners — at the dock, on the water, in the engine room, on the radio. Some are technical. Some are operational. A few are conventions that don't appear in any official publication but that every working captain knows.
The definitions are written for owners, not for the Coast Guard exam. Where a term is covered in more depth in one of our articles, we've linked to it.
If a term you're looking for isn't here, let us know and we'll add it.
A · B · C · D · E · F · G · H · I · K · L · M · N · O · P · R · S · T · V · W · Y
A
Aft Toward the back of the boat. The opposite of forward. The aft end of a vessel is the stern.
Anchor bridle A two-legged line attachment that connects the anchor rode to the boat at two points on the bow rather than one. Spreads load, reduces shock-loading, and keeps the boat from yawing back and forth at anchor. On larger cruisers, a bridle is the difference between sleeping well at anchor and getting up at 2 a.m. to check the set.
Anchor light The white light displayed at the highest point of a vessel at anchor between sunset and sunrise. Required by the Navigation Rules. Often forgotten by recreational boaters anchoring overnight in protected anchorages.
Anchorage A body of water with adequate depth and protection where vessels customarily anchor. A good anchorage offers protection from the prevailing weather, holding ground appropriate to the anchor type, and enough swing room for the rode you'll let out.
AIS (Automatic Identification System) A radio-based identification and tracking system used on commercial vessels and many recreational ones. Broadcasts vessel name, position, speed, and heading on dedicated VHF frequencies. Receivers display nearby AIS-equipped vessels on a chart plotter screen. Particularly useful in commercial traffic.
B
Beam The width of a vessel at its widest point. A boat with a 14-foot beam is fourteen feet wide. Also used to indicate direction — a "beam wind" is one coming from directly off the side of the boat.
Bow The front of the boat. The opposite of the stern.
Bow line The dock line that runs from the bow of the boat to the dock. Controls fore-and-aft movement at the front of the vessel.
Bridge tender The person operating a drawbridge. The official with authority over when (and whether) the bridge opens for marine traffic. Treated with respect on the radio and during transits. The Detroit River alone has several. See: VHF Radio Etiquette.
Bridle See: Anchor bridle.
C
Channel 13 The VHF channel used for bridge-to-bridge ship navigation communication in U.S. waters. Used by commercial freighters and tugs to coordinate passing arrangements with each other and with smaller recreational craft. Monitored constantly in commercial waters like the Detroit River and Lake Huron.
Channel 16 The international VHF calling and distress channel. Monitored 24 hours a day by the U.S. Coast Guard. Used to initiate contact, then to switch to a working channel for actual conversation. Not a chat channel. See: VHF Radio Etiquette.
Chart plotter The electronic display unit that shows your vessel's position on a digital nautical chart. Most modern recreational boats have one. The good ones integrate GPS, AIS, radar, depth sounder, and route planning into a single display.
Cleat A T-shaped fitting on a dock or a boat used to secure a line. The proper way to tie a line to a cleat is the cleat hitch — a specific knot taught early in any First Mate program. Done wrong, the line slips or jams; done right, it holds firmly and releases easily under load.
Cleat hitch The knot used to secure a dock line to a cleat. Two wraps around the base, a figure-eight pattern across the horns, and a final locking turn under the last wrap. Once you've tied a thousand, you don't think about it anymore. Before that, you think about it every time.
Commercial Towing Assistance Endorsement A USCG credential add-on authorizing the holder to perform commercial towing of disabled vessels — the kind of work TowBoatUS or SeaTow captains do. Required for anyone offering commercial towing services. Captain Tom holds this endorsement on both his 100-ton and 50-ton Master Licenses.
Crew Anyone aboard the vessel other than the captain. In recreational boating, often used interchangeably with "guests" or "passengers." On a working vessel, crew specifically means people with assigned operational responsibilities.
Cruiser A type of recreational boat with overnight accommodations — sleeping quarters, a galley, a head — capable of multi-day use. Distinct from a center console (open-deck day boat) or a sportfish (specialized fishing platform). Most owner-assisted deliveries are on cruisers.
D
Daily rate The standard daily compensation paid to a delivery captain for time spent operating the vessel. Distinct from travel days and layover days, which may be billed at the same or a different rate per the delivery contract.
Deposit A non-refundable payment made by the boat owner to secure the captain's dates for a delivery. Credited against the final invoice. Standard practice in the delivery captain industry; without it, owners can cancel on short notice and leave the captain without work for the dates blocked.
DSC (Digital Selective Calling) A function on modern VHF radios that allows the user to call a specific vessel directly using its MMSI number, rather than broadcasting on Channel 16. Most modern radios have it. Most owners never set it up.
Dock hand The marina staff member who assists vessels with arrival and departure. Catches lines, fends off, provides local knowledge about the slip. Treated with the same professionalism as a tradesperson on your house — they help you when they think you know what you're doing.
Dock line A line used to secure a vessel to a dock. Modern dock lines are typically three-strand nylon or double-braided nylon, sized to the vessel's displacement.
Documentation Federal vessel registration — the alternative to state registration for vessels over five net tons. Documented vessels carry a USCG Certificate of Documentation and display their official number internally rather than on the hull. Required for some commercial operations and many marine insurance policies.
E
Endorsement An add-on credential to a USCG license — for example, the Commercial Towing Assistance Endorsement. Endorsements expand the scope of operations the licensed captain is authorized to perform.
Engine room check The pre-departure inspection of a vessel's engine compartment. Strainers, fluid levels, belts, blowers, bilge condition, fuel filters. Performed before every run. The single most important habit any boat owner can develop. See: What a First Mate Actually Does Before Departure.
F
Fender A cushioned device, typically inflatable or foam, hung between the vessel and the dock to absorb contact. The First Mate's responsibility to prepare, position, and deploy correctly. Floating docks require different fender placement than fixed-piling docks.
First mate The person aboard the vessel responsible for assisting the captain in operations — line and fender handling, lookout, radio operation, and in emergencies, operation of the vessel itself. On recreational boats, often a spouse or family member. On working vessels, a paid crew position. See: First Mate Coaching.
Float plan A document filed with someone reliable on shore before a voyage, stating the vessel's intended route, expected times, and what to do if the vessel doesn't check in as scheduled. Simple, free, and one of the highest-leverage safety practices available to recreational boaters. See: The First Mate's Emergency Playbook.
Force majeure A contractual term referring to events beyond the parties' control — storms, government-ordered closures, acts of God — that excuse non-performance of obligations. Standard clause in any delivery contract.
Forward Toward the front of the boat. The opposite of aft. The forward end of a vessel is the bow.
G
Galley The kitchen aboard a vessel. From the Latin galea. Still called a galley regardless of how modern the appliances are.
Great Loop A continuous waterway circuit through the eastern United States and Canada — Atlantic Intracoastal Waterway, Hudson River, Erie Canal, Great Lakes, Chicago and Illinois Rivers, and the Tenn-Tom Waterway. Approximately 6,000 miles total. Cruisers who complete the full loop are called Loopers. See: Great Loop guide.
Gross Register Tons (GRT) A measure of a vessel's total internal volume, not its weight. USCG captain licenses are rated by GRT capacity — a 100-ton license authorizes operation of vessels up to 100 GRT. Captain Tom holds a 100 GRT Master License for the Great Lakes and Inland Waters, and a 50 GRT Master License for Near Coastal.
H
Hailing port The home port of a vessel as registered with the USCG. Displayed on documented vessels along with the vessel name. Often (but not always) the marina where the boat is actually kept.
Harbor of refuge A protected harbor specifically built or designated as shelter for vessels seeking safety from weather or mechanical issues. Lake Huron has several along its Michigan shoreline — Harbor Beach being the most prominent. See: Crossing Lake Huron.
Haul out The annual removal of a boat from the water for winter storage — done at the end of the cruising season in the Great Lakes, typically October. The opposite of splash or launch in spring.
Head The bathroom aboard a vessel.
Holding ground The bottom material in an anchorage — sand, mud, clay, rock, or grass. Determines how well an anchor will set and hold. Soft mud holds well; rock and grass hold poorly. A good chart and local knowledge tell you what to expect at any given anchorage.
I
Idle speed The lowest forward propulsion speed at which a vessel can be operated under control. Used in no-wake zones, marinas, and close-quarters maneuvering.
Inland Waters USCG-defined waters within or directly adjacent to U.S. land — rivers, lakes, bays, and sounds inside the demarcation lines. A 100-ton Master license for Great Lakes and Inland Waters authorizes operation in these waters but not on the open ocean.
Insurance rider A temporary addendum to a boat owner's marine insurance policy naming the delivery captain as an approved operator for the dates of a specific voyage. Required by most carriers and by all serious delivery captains. See: Why I Won't Deliver Without an Insurance Rider.
K
Knot (unit of speed) One nautical mile per hour. The standard unit of speed on the water. One knot equals approximately 1.15 statute miles per hour. A vessel running at 8 knots is moving at about 9.2 mph.
Knot (line attachment) A method of securing a line to itself, to a cleat, or to an object. Every captain knows a small number of essential knots — the cleat hitch, bowline, clove hitch, and figure-eight stopper being the most commonly used.
L
Layover day A day on a planned delivery during which the vessel is not moved — typically due to weather, mechanical issues, or planned rest. Billed at a daily rate per the delivery contract. Owners sometimes expect layover days to be free; they aren't.
Lee shore A shoreline that the wind is blowing toward, from the perspective of a vessel on the water. The dangerous side. A vessel disabled offshore of a lee shore is being pushed toward the rocks; the same vessel offshore of a weather shore is being pushed away from them.
License (Master) A USCG Merchant Mariner Credential authorizing the holder to operate vessels of specified tonnage on specified waters. The Master license is the highest level of recreational/light-commercial USCG credential. Tonnage and water-area endorsements determine the scope.
Line A rope, once it's on a boat. The terminology distinction matters more to traditional mariners than to most owners, but using "line" rather than "rope" is one of the small marks of someone who has spent time on the water.
M
Marine Mariner Reference Number A unique identifier assigned by the USCG to each licensed mariner. Used on the captain's credential and provided to insurance carriers when securing a rider. Captain Tom's Mariner Reference Number is 2913289.
Marlinspike seamanship The traditional skill set of working with rope and line aboard a vessel — knot tying, splicing, whipping, and line maintenance. From the marlinspike, a pointed tool used in rope work. The term covers the broader category of practical rope handling.
MMSI (Maritime Mobile Service Identity) A unique nine-digit number used to identify a specific vessel for DSC and AIS purposes. Programmed into the radio and tied to the vessel registration. Required for distress alerting via DSC.
N
Near Coastal USCG-defined waters within 200 miles of the U.S. coastline. A Near Coastal license authorizes operation in these waters in addition to (or instead of) Inland Waters, depending on the specific credential. Captain Tom holds a 50-ton Master Near Coastal in addition to his 100-ton Master Inland.
No-wake zone A water area in which vessels must operate at idle speed, producing no wake. Typically marked with regulatory buoys. Common in marinas, harbor approaches, and protected anchorages.
O
Owner-assisted delivery A delivery model in which the boat owner rides along with the hired captain, learning the vessel through hands-on operation under the captain's coaching during the trip. Combines a standard over-water delivery with on-water coaching. See: Owner-Assisted Boat Delivery.
P
PFD (Personal Flotation Device) A life jacket or other flotation garment. USCG requires one wearable PFD aboard for every person on the vessel, plus a throwable Type IV on boats 16 feet and longer. Wearing one is the First Mate's leadership responsibility — they go on first, so everyone follows.
Port (direction) The left side of the boat, looking forward from the helm. Marked with a red navigation light at night. The opposite of starboard.
Port (place) A harbor, marina, or destination where a vessel calls.
Pre-departure walkthrough The structured pre-trip inspection of the vessel performed by the captain and first mate together. Covers engine room, safety gear, lines and fenders, radio check, and trip plan review. The single highest-leverage activity in any voyage. See: What a First Mate Actually Does Before Departure.
Prop walk The lateral movement of a single-screw boat's stern when reverse is applied. Caused by asymmetric thrust from the propeller. Predictable for a given boat, and useful in close-quarters maneuvering once a captain learns to read it.
R
Rode The line, chain, or combination connecting the anchor to the boat. The scope (length of rode relative to water depth) determines how well the anchor sets and holds.
Running lights Navigation lights displayed by a vessel underway between sunset and sunrise. Red on port, green on starboard, white on stern (for vessels under 50 meters). Required by the Navigation Rules.
S
Scope The ratio of anchor rode let out to water depth at the anchor location, including height of bow above water. A 5:1 scope means five feet of rode for every foot of depth. Higher scopes hold better; lower scopes are sometimes necessary in crowded anchorages. Most captains run 5:1 to 7:1 in normal conditions.
Securité (pronounced say-cure-ee-tay) A VHF safety message used to broadcast a navigation hazard or non-emergency safety information to other vessels. Less urgent than Pan-Pan, dramatically less urgent than Mayday. See: VHF Radio Etiquette.
Set (the anchor) The process of confirming that the anchor has dug into the bottom and is holding. After paying out scope, the captain typically puts the engine in reverse and gently loads the rode to verify the set.
Slip A docking space in a marina, typically with a wooden or floating finger pier on one or both sides.
Souls on board (SOB) The total number of people aboard a vessel. Used in float plans, distress calls, and Coast Guard communications.
Spring line A dock line that runs diagonally between the boat and the dock, controlling fore-and-aft movement. The most important line on the boat in any docking other than a perfect calm-water approach. Used by the captain to spring the bow or stern off the dock during departure. Often misunderstood by new boaters and underused.
Starboard The right side of the boat, looking forward from the helm. Marked with a green navigation light at night. The opposite of port.
Stern The back of the boat. The opposite of the bow.
Stern line The dock line that runs from the stern of the boat to the dock. Controls fore-and-aft movement at the back of the vessel.
T
Throwable PFD A Type IV personal flotation device — typically a cushion or ring — designed to be thrown to a person in the water rather than worn. USCG-required on vessels 16 feet and longer.
Trim tabs Adjustable plates on the transom of a powerboat that change the boat's running attitude in the water. Used to compensate for load distribution, wind, and sea state. Most owners use them too little; a few use them too much.
Trip plan The intended route and schedule of a voyage — including departure time, waypoints, expected port arrivals, and contingency anchorages. Distinct from a float plan, which is the document filed with someone on shore.
V
Vessel delivery The professional service of transporting a boat over water from one location to another, performed by a USCG-licensed captain. Distinct from boat transport (trucking) and from charter (passenger service). See: Vessel Delivery.
VHF (Very High Frequency) The radio frequency band used for marine communications. Most marine VHF radios operate between 156 and 174 MHz. Limited to roughly line-of-sight range — typically 10 to 20 miles depending on antenna height. See: VHF Radio Etiquette.
W
Wake The disturbed water trailing behind a moving vessel. Vessels are legally responsible for their wake — meaning damage caused by a wake to other vessels, docks, or shoreline property is the responsibility of the vessel that produced it.
Weather shore A shoreline that the wind is blowing away from, from the perspective of a vessel on the water. The protected side. The opposite of a lee shore.
Whistle (signal) A standardized sound signal used between vessels to indicate passing intentions in restricted visibility or close-quarters maneuvering. "One whistle" indicates a port-to-port passing; "two whistles" indicates starboard-to-starboard. Used today on Channel 13 voice radio calls more often than as actual horn signals.
Y
Yard A boatyard — the facility where vessels are hauled, stored, repaired, and serviced. The term carries the same connotation as a "shop" in automotive terminology.
Closing
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