I'd like to see their source for that! "[He] sleep[s] with the fishes" is the canonical form of the idiom, whose presence in the common vernacular originates w

I'd like to see their source for that! "[He] sleep[s] with the fishes" is the canonical form of the idiom, whose presence in the common vernacular originates with its use in Puzo's "The Godfather"; in my entire life as a native US English speaker, I have never once heard "swim with the fishes" used with anything remotely resembling the same meaning. (It doesn't even make sense! Dead things don't swim; they can't, because they're dead.)