The Nantucket Lightship LV-117 was a lightvessel

Lightvessel

A lightvessel, or lightship, is a ship which acts as a lighthouse. They are used in waters that are too deep or otherwise unsuitable for lighthouse construction...

 of the United States Lighthouse Service

United States Lighthouse Service

The United States Lighthouse Service, also known as the Bureau of Lighthouses, was the agency of the US Federal Government that was responsible for the upkeep and maintenance of all lighthouses in the United States from the time of its creation in 1910 until 1939...

, operating off of Nantucket Shoals

Nantucket Shoals

Nantucket Shoals is an area of dangerously shallow water in the Atlantic Ocean that extends from Nantucket Island, Massachusetts, eastward for and southeastward for ; in places water depth can be as shallow as . Depth soundings are unpredictable due to constant change from strong currents. The...

. She was operated for only three years, from 1931 to 1934, before she was sunk in a collision with the RMS Olympic

RMS Olympic

RMS Olympic was the lead ship of the Olympic-class ocean liners built for the White Star Line, which also included Titanic and Britannic...

, the sister-ship of the RMS Titanic. Seven of the eleven crew members on board at the time of the sinking were killed. It was replaced by the United States lightship Nantucket (LV-112)

United States lightship Nantucket (LV-112)

The United States lightship Nantucket , also known as Lightship No. 112, Nantucket, is a National Historic Landmark lightship that served at Lightship Nantucket position...