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Nautical Term Glossary

Boating, like many other activities, comes with its own set of terms, phrases, and definitions. Many of these are centuries-old, used for clear communication to the crew for safety, docking and operation. 

So why don't boaters just say front, back, left, and right? The answer is that the starboard side is ALWAYS the starboard side, no matter which way you, or anyone else, is facing on board. This is important. Imagine that you're on a boat and the captain asks you to quickly put fenders over the right side. If you were facing one another, would that be your right or theirs? Or imagine it's getting dark, or heavy weather is upon you, and you can't see which way people are facing on the boat. Saying "It's to your left!" or "Look to the right!" would make no sense to anyone and would create confusion that could threaten the crew and boat. If someone yells, "Man overboard! Port side!" Clear directions and the use of accurate terms could mean the difference between locating or losing sight of, a victim.

The partws of an open cabin motorboat

The parts of a sailboat

The parts of a canoe


AMIDSHIPS -Center of the boat with reference to its length and/or sometimes its width.
AFT -Toward the stern of a boat.
ASTERN - Behind or near the stern of a ship/boat (also used for aircraft)
BEAM -The boat's maximum width.
BILGE - Lower internal part of a boat's hull.
BOAT - All watercraft, including a seaplane on the water but not in flight, used or capable of being used as a means of transportation on the water. Exemptions include boathouses, floating homes, air mattresses, beach and water toys, or single inner tubes.
BOW - The forward part of a boat.
DRAFT - The depth of the boat below the water line is measured vertically to the lowest part of the hull.
FORE - To or at the front of the boat.
FREEBOARD - The height of the boat's side measured from the waterline to the deck or gunwale.
GUNWALE - The upper edge of the side of a boat or ship.
HULL - The body of a boat.
MOTORBOAT - Any boat propelled in whole or in part by machinery, including boats temporarily equipped with detachable motors. These include gasoline and electric motors.
PORT - The side of a boat to the left when facing the bow.
PERSONAL WATERCRAFT - Commonly known by brand names such as Jet Ski or Wave Runner, a PWC is a motorboat using a water jet pump as its primary propulsion. designed for operation by a person sitting, standing, or kneeling.
PROPULSION - The mechanism or system used to generate thrust to move a watercraft through the water. 
SAILBOAT - Any boat that is under sail alone, including any sailboat equipped with a motor.
STARBOARD - The side of a boat to the right when facing the bow.
STERN - Back end of a boat. 
TRANSOM - Flat planking across the stern of a boat.
UNDERWAY - Boat in motion. Technically, a boat is underway when not moored, at anchor, or aground.
VANE - A broad blade attached to a rotating axis or wheel which pushes or is pushed by wind or water and forms part of a machine or device such as a foilwindmillpropeller, or turbine.


CURRENT – An ever-present flow of the water - from timid to turbulent –where volume, channel width, and gradient (see definition below) all affect the characteristics of a river. Current is usually slower along the inside bend of a river, and faster along the outside bend. Also current is faster on the surface due to less friction than along the bottom of the channel.

GRADIENT – The steepness of the riverbed, expressed in feet/mile (an average).

RAPIDS – water flowing over an obstruction, causing turbulence. Most often formed by boulders below the surface.

HOLES – water flowing over a ledge or rock creating a void, can trap objects held in the circulating flow/hydraulics created.

HYDRAULICS – Water circulating on top of itself – evident by the churning of water below a dam or spillway. Often associated with other hazards such as holes and breaking waves.

EDDIES – Water rushing around obstacles/obstructions, circulating downstream, towards shore in a reverse current. Current flows to fill the void created by the flow of water. Sometimes violent eddies form whirlpools.

EDDYLINE – the boundary between the circular eddy and the downward current flow.

POUROVER - Think of it as a vertical eddy, water flowing over a rock, ledge or manmade horizontal structure (dam, spillway, weir) creating a "hole" below the obstruction.

DROP – Water dropping straight down – a waterfall is a classic example.

CONSTRICTED WAVE – As flowing water is constricted – by a narrowing channel - it begins to move faster. The compressed water sometimes forms waves.

WAVETRAIN – a series of non-breaking waves.

BREAKING WAVES – the top of a swell that collapses down on the upstream side of the wave (often referred to as a "stopper").

*River Glossary from