The life cycle of the shore fly (Scatella tenuicosta) has the following stages: egg, three larval instars, a pupa and the adult fly. The eggs are laid singly and are bean-shaped. A first instar larva is translucent white. Second instar larvae are brownish, less translucent and their body is cylindrical. The larvae are found in the top layer of damp soil, where they also pupate.
The adult shore fly is black, about 4 to 5 mm long, and stout with short antennae and short legs. The head of the adult has a pair of conspicuous eyes. The wings have grey-brown patches.
Although shore flies can occasionally be confused with sciarid flies (Bradysia paupera & Lycoriella ingenua), they are more stoutly built and have shorter antennae without beads.