Yellow water lily - Nuphar lutea

I don't think there's much that you could mistake this species with. There's a similar species called least water lilly but this plant has flowers that are less than 4cm whereas N.lutea has flowers larger than 4cm. I found this growing in the lake at Wood's Mill.

Just took this picture (16Jun07) and thought i'd include it in this post as you get a much better shot of the picture. This flower was seen at the lake in Abbot's wood.