Denton raft
The Denton raft was a buoyancy aid to enable life-saving. It was a square of cork, approximately, with an aperture in the middle and rope attachments to which sailors could cling. It was widely used by Royal Navy ships during World War II. HMS Hood was, for example, equipped with numerous Denton rafts. It was three Denton rafts that allowed the three survivors to survive. The rafts were sometimes nicknamed biscuit rafts.