ID Help needed

ID Help needed

Observation - ID Help needed - UK and Ireland. Description: An erect plant growing in shallow flowing water in woodland, 150mm tall. Pinnate leaf consisting of 7 leaflets lower down, but 5 leaflets higher up. Small white flowers, 4 petals, 6 stamens. Any help would be greatly appreciated.

An erect plant growing in shallow flowing water in woodland, 150mm tall. Pinnate leaf consisting of 7 leaflets lower down, but 5 leaflets higher up. Small white flowers, 4 petals, 6 stamens.
Any help would be greatly appreciated.