A lightvessel, or lightship, is a conventional ship which acts as a lighthouse. It has no means of propulsion and is permanently anchored. It is used in waters that are too deep for a lighthouse, and instead of marking coastlines, usually marks marine traffic routes. It is superior to a buoy because it has much stronger navigational aids.

Lightvessels also usually carry data recorders used in oceanography for research purposes, such as wave recorders.

In England and Wales, Trinity House is in charge of all lightvessels. All are now unmanned, but had nine crew in the past. As of 2003, there are 14 lightvessels and 2 smaller lightfloats. The first lightvessel was converted to solar power in 1995, and more are due to be converted.

The official use of lightships in the United States ended March 29, 1985, when the U.S. Coast Guard decomissioned its last such ship, the Nantucket I. Many lightships were replaced with offshore light platforms (called "Texas Towers") or large navigational buoys - all of which are cheaper to operate, build and maintain than lightships.

"Lightvessel" in other languages: German Feuerschiff, Danish Fyrskib, Swedish Fyrskepp...

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See: List of lighthouses and lightvessels, Lightvessels in the United Kingdom...

de:Feuerschiff pl:Latarniowiec sv:Fyrskepp