Glossary Archive

Chop

Short choppy seas


Chronometer

A highly accurate timekeeping instrument, specifically designed for determining longitude at sea. A chronometer is a precision timepiece used aboard ships to aid in navigation by providing an accurate measure of time, which is crucial for determining a vessel's longitude. Before the invention of the marine chronometer in the 18th century, sailors had no reliable...


Clean Bill of Health

⚓ Nautical Origin of A Clean Bill of Health: Back in the 18th and 19th centuries, when ships traveled from port to port, they could carry more than just cargo—they might also bring diseases like cholera, plague, or yellow fever. To prevent outbreaks, port authorities began requiring ships to present a “bill of health”—an official document from the last port of...


Clear

A section of water that is free from obstructions, hazards, or any other vessels. In the context of marine terminology, clear water is a term used to describe a body of water that is free from any obstructions, hazards, or other vessels. This could include anything from rocks, reefs, and sandbars to other boats, buoys,...


Clear

Refers to conditions at sea where visibility is good, the sky is mostly free of clouds, and there are no immediate threats of severe weather events. In greater detail, clear weather is a term used in marine contexts to describe optimal weather conditions for navigation and other maritime activities. This typically includes a sky that...


Clear

To disentangle a line, for example, removing it from a dock cleat when manoeuvring out of a marina. When departing from a mooring, it is good practice to give the instruction 'Clear', indicating that the line is free from its attachment and out of the water. This avoids potential entanglement in the vessel's propeller and informs...


Clearance

The distance between top of mast and bridge or bottom of keel and seabed.


Cleat

A fitting on a boat or dock used to secure a rope or line. A cleat is an piece of hardware found on boats, docks, and other marine structures, designed to secure lines or ropes. Typically, a cleat is made of metal, such as stainless steel or aluminium, or durable plastic, and it features two...