HMHS Britannic was the third, last-built and largest member of the White Star Line’s Olympic class of vessels. She was the sister ship of RMS Olympic and RMS Titanic and was intended to enter service as the transatlantic passenger liner, RMS Britannic.
Britannic was launched just before the start of the First World War and was laid up at her builders in Belfast for many months before being put to use as a hospital ship in 1915. On the morning of 21 November 1916, she was shaken by an explosion, caused by an underwater mine, in the Kea Channel off the Greek island of Kea and sank 55 minutes later, killing 30 people.
There were 1,065 people on board; the 1,035 survivors were rescued from the water and lifeboats. Britannic was the largest ship lost in the First World War. The wreck of HMHS Britannic is in about 400 feet (122 m) of water. It was first discovered and explored by Jacques Cousteau in 1975.