Bogbean

Now for something different. Bogbean (Menyanthes trifoliata) is a perennial which grows in ponds, bogs and fens. It has stout creeping runners and rounded floating leaves.
Here it is thriving in the pond in Knottman's garden. If you want to see it in the wild try White Moss Common between Rydal and Grasmere.
Yet another try for an extra photo. If it works it is an amusing notice in the First Class toilet on Virgin trains.