backswimmer

[ bak-swim-er ]
/ ˈbækˌswɪm ər /

noun

any of numerous predaceous aquatic hemipterous insects, of the family Notonectidae, that swim on their backs, and may inflict a painful bite if handled.

Origin of backswimmer

First recorded in 1860–65; back1 + swimmer
Also called boat bug.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019