Commander Lionel 'Buster' Crabb was a Royal Navy frogman who died during a Cold War spy operation in Portsmouth.
Notes on verification
Well corroborated by Wikipedia, MCDOA, and HistoryNet regarding the mission and disappearance, but Crabb's death was never conclusively confirmed — he was declared presumed dead, and a headless/handless body found later was only presumed to be his. The claim states he 'died' as fact, which slightly overstates the certainty of the historical record.