The family consists of about 200 species in 5 genera, distributed wherever there is freshwater habitat; it is the only extant member of superfamily Haliploidea.

[1][2] The compound eyes are markedly protruding from a smallish head, which bears antennae with 11 segments set upon an antennophore with a conspicuously short base (scapus).

The maxillae and labium are adapted to manipulating the algae the larvae feed on, while the mandibles contain a channel through which fluids are sucked out of the food.

The larval legs are short and carry a single claw each, but the forelegs have various adaptations for climbing among water plants.

Respiration is via gills which are either long and filamentous, or (in Peltodytes) short microtracheal extensions; they are carried on the tergites of all sternal and all but the tenth (last) abdominal segments.

Hungerford's crawling water beetle (Brychius hungerfordi) is an endangered species found only in Michigan and Ontario.

The others have more synapomorphies in common; Haliplus is the more diverse and appears to include some minor lineages formerly considered independent genera.