Shell minute to small, usually 1-10 mm in height (but up to 50 mm), dextrally coiled, planispiral to aciculate, phaneromphalous to cryptomphalous, with about 2-8 whorls. Body whorl often loosened, shell sometimes partially uncoiling to assume a corkscrew or horn-like shape. Shell thin to fairly solid, transparent to white. Periostracum generally thin, rarely elaborated as hair-like or other projections; often colored, usually uniformly but rarely with band-like patterns. Aperture holostomatous, sometimes thickened, sinuous, deflected or flared, but without notches, canals, siphonal grooves, or denticulations. Shell usually smooth except for collaboral growth-lines, but occasionally with sculpture of reticulations, carinae, spines, or cords. Protoconch usually paucipsiral, rarely multispiral, usually dome-like, smooth or with sculpture of wrinkles, pits, or spiral lines.
Operculum usually well-formed, rarely rudimentary, corneous, usually paucispiral, rarely multispiral or conical. Ventral (very rarely dorsal) opercular surface sometimes with elevated corneous or whitened (calcareous?) ridges or pegs.
Head-foot, mantle, and visceral coil often pigmented externally with melanin granules ranging from pale grey to dark purple-black; yellow granules rarely present Cephalic tentacles sometimes with transverse pigment bars, eyes often ringed with internal patch of yellow hyaline granules. Internal organs and structures variously colored. Subterranean animals often completely unpigmented.
Foot strong, mobile, retractile into shell, truncate anteriorly, rounded behind, with lateral auriculate lobes, without suprapedal fold and omniphoric grooves. Anterior mucous glands discharging through narrow groove across anterior edge of foot; posterior mucous glands absent Pedal tentacles, lobes, or cirri absent. Movement by ciliary gliding. Cephalic tentacles filiform, with parallel sides and blunt or rounded tips, usually circular in cross-section. Eyes in bases of tentacles, usually in discrete swellings on outer sides. Tentacles usually symmetrical, often with patches or tracts of ciliary tufts (combinations of motile and non-motile) on dorsal and/or ventral surfaces. Head, floor of pallial cavity also sometimes strongly ciliated. Mantle edge rarely papillate or with a single pallial tentacle. Mantle cavity floor smooth, without ridges.

Animal having a long rostrum ; tentacles elongated, with the eyes at their outer bases. Ctenidium monopectinate ; sexes separate ; the intromittant organ distant from the right tentacle, and generally appendiculated ; one otolith in each otocyst. Jaws are usually pre¬sent. Formula of teeth of radula 2+1+1 + 1 + 2; the central tooth mostly with basal denticulations.
Shell with a prominent spire, turbinate or turriculate ; peristome continuous; operculum variable, horny or calcareous, concentric, spiral or subspiral.
The Hydrobiidae are small oviparous molluscs, living in fresh or brackish water, some of them even, though branchiferous, out of the water.