I think I am right in saying that there are no native British species of white water-lilies (Nymphaea agg). Imported for water gardens in past times they have established themselves in ponds and lakes pretty much everywhere; indeed we have them in our garden pond. There are various species you may encounter, mainly of the family Nymphaea and rather then attempt to write abut all of them I have grouped themselves together which is where the agg. in the scientific name comes from - aggregated.
Although introduced there do seem to good for native wildlife. Hoverflies, dragonflies and damselflies like to bask on the leaves which are also popular with pond skaters who want to haul themselves off of the water surface for some personal grooming. Water snails are frequent on the undersides of the pads and frogs often hide by them whilst cooling off in the heat of the day. I am not sure the flowers are quite so beneficial as the leaves but they do add a touch of glamour!I believe the species in my photograph is Nymphaea alba which is one of the most common.
White Water-lily: padded up