Perennial or rarely annual, aquatic or swamp herbs, with rhizome or stolon, monoecious (rarely dioecious) or with bisexual flowers. Leaves basal, subdistichous, usually erect and emergent, sometimes floating or submerged, usually petiolate (except for submerged leaves). Inflorescence emergent, racemose or panicle-like, with ultimate flowering units usually in cymose pseudo-whorls, individual flowers and pseudowhorls separated by long internodes, basally with a long, slender non-flowering axis, or flowers solitary in Hydrocleys. Flowers bisexual or often unisexual; perianth of 2 whorls of 3 segments each, the outer whorl often green; inner whorl white, pink or purple; stamens 3 (not in Victoria), 6 or numerous; carpels usually free, except united at base, usually numerous; ovules usually 1, except 2 or more in Damasonium and Hydrocleys. Aggregate fruit of achenes (hence, indehiscent) or follicles (hence, dehiscent in Damasonium and Hydrocleys).
Cosmopolitan, c. 110 species in 15 genera; 8 genera and 14 species occur in Australia; 4 genera and 6 or 7 species in Victoria.
Alismataceae has recently been re-circumscribed to include Limnocharitaceae due to a lack of apomorpic characters when these other genera are considered in Limnocharitaceae.
The unisexual flowers are probably derived from bisexual flowers, being functionally unisexual by abortion.