sleep with the fishes

Earliest known record is from 1833, see the quotation below. The phrase was popularized in the motion picture The Godfather (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.^[1]

• Audio (General Australian):

  (file)

sleep with the fishes (third-person singular simple present sleeps with the fishes, present participle sleeping with the fishes, simple past and past participle slept with the fishes)

1. (idiomatic) To be dead, with one's corpse disposed of in a body of water.
   • 1833 March, “The Three Humpbacks ; or, the Bridge of Bagdad”, in The Lady's Magazine and Museum‎^[1], page 105:

     The porter […] opened his sack, and pitched the corpse into the river, and ran back to receive the rest of his pay “ It is done,” said he, laughing ; “ Your man sleeps with the fishes of the Tigris by this time […] ”

• Davy Jones's Locker