Shell transparent, glossy, with five or six markedly tumid whorls, no visible ornamentation (fine growth lines may be seen on closer inspection); last whorl comprising >50 % of shell height, not angulate at periphery. Aperture egg-shaped, with thin peristome; outer lip abuts almost at right angles to last whorl, slightly flared basally, though less so than in Hydrobia ulvae , inner lip reflected over umbilicus, leaving a shallow groove (V. ventrosa-drawing).
Up to 5 x 2 mm.
Shell colour as in Hydrobia ulvae : periostracum horn-coloured, underlying shell white; viscera showing through apical whorls gives living shells a darker appearance.
Body similar to Hydrobia ulvae but lacks dark transverse band on snout; no dark ring on tentacles, instead a dark dorsal line often present near tips. Penis smaller than in H. ulvae , with a narrow flagellate tip.
Not as common as H. ulvae , occurs in more brackish waters, preferring isolated lagoons, creeks, and ditches to open coasts.
Patchily distributed from the Baltic to the Mediterranean and Black Sea (Distr. V. ventrosa).