Foliage of what is thought to be Berula erecta / Lesser Water-Parsnip but could be Fool's Watercress / Apium nodiflorum in drainage ditch. SEE NOTES

I am uncertain whether this is Berula erecta, or another semi-aquatic plant called Fool's Watercress / Apium nodiflorum syn. Helosciadium nodiflorum. There is a similarity between the habitats and physical appearance of the two species so please verify before use. The plant seen could even be a wild form of Watercress since a patch of similarly leaved plants nearby developed white Cruciferae flowers - Apium and Berula belong to the Umbellifer / Apiaceae family which have a different flower-head structure.