Glossary Archive

The UK government agency responsible for producing nautical charts, publications, and navigational information to support safe maritime navigation.  The UK Hydrographic Office is an executive agency of the UK Ministry of Defence, providing hydrographic and geospatial data for both military and commercial maritime use. It produces and maintains Admiralty charts and publications, which are widely...

The UK government agency responsible for producing nautical charts, publications, and navigational information to support safe maritime navigation.  The UK Hydrographic Office is an executive agency of the UK Ministry of Defence, providing hydrographic and geospatial data for both military and commercial maritime use. It produces and maintains Admiralty charts and publications, which are widely...

Flag semaphore indicating the letter U.

International Morse Code sequence representing the letter U.

Ultraviolet (UV) light is a type of electromagnetic radiation with a wavelength shorter than visible light but longer than X-rays. In the marine context, UV radiation from the sun can have various effects on the marine environment, including damaging coral reefs, affecting marine organisms, and degrading marine materials exposed to sunlight. UV radiation is also...

An international organisation founded in 1945 aimed at promoting peace, security, and cooperation among countries worldwide. The United Nations (UN) was established after the Second World War with the primary objective of preventing future conflicts on a global scale. It serves as a platform where representatives from nearly every country can come together to discuss...

A loop which crosses under the standing part of a rope when tying a knot.

Under the weather is commonly used to describe feeling ill or unwell. Its origins can be traced back to maritime language. It originated from the maritime world in the early 1800s. When sailors were seasick or unwell, they would go below deck to escape the weather and recover. The original phrase was "under the weather bow", which...

Underway refers to vessels not anchored or made fast to the shore (for example, a marina or mooring buoy). The vessel may be moving due to the impact of the tide or windage but not under its own means of propulsion. When under its own propulsion, a vessel is described as Making Way. This is...

Pronounced: YOU-nee-form The term for the letter U in the NATO Phonetic Alphabet.