Number of species:34
Thirty-one small (1-3mm) species in Britain, of various body shapes: Hydraena and Octhebius are similar to Helophoridae in general appearance (though without the striate pronotum or extended palps), while Limnebius are more smoothly rounded, akin to Tachyporus species (Staphylinidae). All crawlers rather than swimmers, they are nevertheless found in and near waterbodies, including in brackish water (particularly Ochthebius). Many of the aquatic species occur in silt and vegetation at the edges of waterbodies (especially Limnebius species), although several occur in fast-flowing water (particularly Hydraena). Males of Limnebius and Hydraena have spectacular genitalia.