These are known as shore bugs, and are a family of insects in the order Hemiptera (true bugs). They are oval-shaped and measure 2.1 8.2 mm long when mature. They are usually found near shorelines or the marginal growths near water. They are able to escape harm by leaping or taking flight.
MacCafferty, W. Patrick (1983). Aquatic Entomology: The Fishermen's and Ecologists' Illustrated Guide to Insects and Their Relatives (1st ed. ed.). Jones & Bartlett Publishers. . p. 345.