Green’s Dictionary of Slang

(US black) a cunnilinguist; thus deep-sea diving, cunnilingus.

1928		Bessie Smith ‘Empty Bed Blues Part 1’ 🎵 He’s a deep-sea diver / with a stroke that can’t go wrong, / He can touch bottom, and his wind holds out so long.
1992		S. King Gerald’s Game (1993) 199: She had called it ‘deep-sea diving with the long white pole’. [Ibid.] 259: It was maybe a little weird to get turned on by the idea of locking your wife up in handcuffs before going deep-sea diving with the long white pole.