Alisma plantago-aquatica Water-plantain C DD N
This water plant is fairly common in England, Wales, Ireland and southern Scotland so it is quite easy to find in local ponds but the secret of getting anything like a decent photo is to find one on drying mud so you can stand right next to it. It is one of those plants the flowers of which are small compared with the size of the plant so they don't show up in a whole plant photograph. The flowers are three petalled which makes this plant easy to identify.