Troy, it looks like Marsh Marigold to me.(Caltha Palustris)
See the link below for more info.
"Horton"

Here is a link that might be useful: Marsh Marigold (Caltha palustris)

Spatterdock?

Cath, I think you are right and it is Splatterdock.
I didn't think that Splatterdock stemS rose up from the water surface, as we see in Troy's photographs.
I bow to your knowledge. If was Marsh Marigold it should have it's Buttercup like flowers on the plant by now.
"Horton"

It is Spatterdock. I have it and last year, I was able to get a dying bloom that made a seed pod but I don't think the seeds were viable. The flowers can get almost as big as a tennis ball. Well, at least in Florida they can.

Horton They actually do have yellow flowers forming. I just was unable to get them in the picture using my cellular phone. Lets face it cell cams are not the best for much of anything other then quick shots with no detail.

troy

Hi Troy, Splatterdock also has a yellow flower, you can see it in the photograph linked below.

"Horton"

Here is a link that might be useful: Splatterdock flower

;) I had to laugh when I saw the pics, because "Splatterdock" pond lilies are super-abundant around here, where I live. (I live in Western Washington state.) I had dug a small earth pond about ten years ago, and transplanted several of the plants from nearby ponds into my own pond. Only one lived. It barely survived year after year, probably because the pond was nutrient-poor. I did have a few trout in there, but a heron ate them. It became just another frog pond, which was cool, but I really wanted to see the lillies grow. Eventually I planted pondweed in there, to give cover for any future fishes. That was probably a mistake, because this pondweed can be very invasive and a great pest. However, all of a sudden just this last year I suddenly saw green leaves grow on the bottom of this pond all over it. Apparently I finally got a good yellow flower out of the one surviving lilly, and the seeds had been distributed all throughout the pond. It is now in serious competition with the pondweed. Yea! Now, I'll have lots of pond lillies, and later, lots of fish that will survive heron attacks! ;)
randy