Not to be semantically confused with : Great Water-parsnip (Sium latifolium nor with Wild Parsnip (Pastinaca sativa) nor with Parsley Water-Dropwort ((Oenanthe lachenalii) nor with Garden Parsley (Petroselinum crispum) nor with Milk-parsley (Thyselium palustre) nor with Fool's Parsley (Aethusa cynapium), Cow Parsley (Anthriscus sylvestris), Upright Hedge-Parsley (Torilis japonica), Stone Parsley (Sison amonum), Corn Parsley (Petroselinum segetum) [all plants with similar names belonging to the same Umbellifer Family (Apiaceae)].

Easily mis-identified as : Fool's-Water-cress (Apium nodiflorum) but distinguished from that by the presence of 4-7 bracts under the main umbel, and by the distinct node in the lower leaf-stalk of the basal pinnate leaves.

It is a sprawling to erect native stoloniferous perennial which grows in or beside shallow freshwater or in Fens or on Marshes and is the only plant in its genus, Berula.

It contains the toxic polyacetylenes (aka polyynes) Falcarindol (21.5%) and Falcarindiol, and the sesquiterpenoid β-SesquiPhellandrene (17%), β-Caryophyllene (15%) and γ-Terpinene (15%) which were present in the essential oil at the relative concentrations shown. The roots are apparently rich in Coumarins.

Unlike many umbellifers with harmaphrodite flowers on the inner umbels and male flowered outer umbels, all Lesser Water-parsnip umbels have hermaproditic flowers. The flowers are white, not tinged pink (although anthers are pink/red if seen without the cream-coloured pollen).