That looks like a Woods White Knight. (By Jack Wood) I dug a few up in our retention pond at work, potted up a BIG one 2 weeks ago, and this week, it rewarded me with 2 HUGE blooms. ( I gave it 5 tabs...)If the pads are very scalloped, and ruffled, somewhat thick, with purplish thick stems, then that would be my guess. Funny too, one just landed in my personal pond last night....the lily fairy.
It stays open here until noon, opens later-after I go home at 5. Perfect for my home pond, since I never see the day blooms anymore. I can't wait for my first bloom at home!! Anywho, here are a couple of pix from the work pond, and one which you can see the pads better-
