The Collaborative International Dictionary
Water bug \Wa"ter bug`\ (Zo["o]l.)
The Croton bug.
Any one of numerous species of large, rapacious, aquatic, hemipterous insects belonging to Belostoma, Benacus, Zaitha, and other genera of the family Belostomatid[ae]. Their hind legs are long and fringed, and act like oars. Some of these insects are of great size, being among the largest existing Hemiptera. Many of them come out of the water and fly about at night.
Wiktionary
alt. 1 Any member of the infraorder ''(taxlink Nepomorpha infraorder noshow=1)'', the (vern true water bug pedia=1)s. 2 Any of various other true bugs that live around water. 3 The American cockroach, (taxlink Periplaneta americana species noshow=1). 4 The oriental cockroach, (taxlink Blatta orientalis species noshow=1). n. 1 Any member of the infraorder ''(taxlink Nepomorpha infraorder noshow=1)'', the (vern true water bug pedia=1)s. 2 Any of various other true bugs that live around water. 3 The American cockroach, (taxlink Periplaneta americana species noshow=1). 4 The oriental cockroach, (taxlink Blatta orientalis species noshow=1).
WordNet
n. a true bug: large aquatic bug adapted to living in or on the surface of water
small light-brown cockroach brought to United States from Europe; a common household pest [syn: German cockroach, Croton bug, crotonbug, Blattella germanica]
Usage examples of "water bug".
Jedra got a sudden idea and went back to the cooked water bug, broke off another leg, and brought it back to the edge of the ocean.
He slowed down in time, let go of the mast, and staggered about in a little erratic circle, dizzy as a water bug until he slumped to the deck and lay there.
But this time, the semi-nude figure of Goldie Lesher floated on the ripples down there, arms and legs extended like some kind of dead water bug, face buried under water.
Then it started sliding around drunkenly, darting and stopping like a water bug, spinning, tearing up trees.