boat bug Meaning, Definition & Usage

  1. noun carnivorous aquatic bug having paddle-like hind legs
    water boatman.

WordNet

Boat" bug`
Definitions
  1. (Zoöl.) An aquatic hemipterous insect of the genus Notonecta; -- so called from swimming on its back, which gives it the appearance of a little boat. Called also boat fly, boat insect, boatman, and water boatman.

Webster 1913