sleep with the fishes

Etymology
Earliest known record is from 1833, see the quotation below. The phrase was popularized in the motion picture  (1972). The 1969 book on which the movie was based includes a large, dead fish wrapped in a bulletproof vest being used to signify that a character is "sleeping on the bottom of the ocean", but not the phrase.

Verb

 * 1)  To be dead, with one's corpse disposed of in a body of water.