Beetle

It is not a beetle, it is a true bug (Order: Hemiptera Suborder: Heteroptera) and this is identified by the triangle at the rear where the wings fold over one another (they do not overlap in beetles, only in true bugs). Based on body shape and the legs it is certainly in Infraorder Nepomorpha, Family Belostomatidae (giant water bugs), Genus Lethocerus. I am guessing L. americanus and it is aptly named the Giant water bug or sometimes the Toe-Biter :-)

Looks some kind of predaceous diving beetle, judging from the hind and front legs. It can inflict a nasty pinch.