They July AMA magazine has a lot of information about float flying. Trainers tend to make excellent float flyers, but make sure you don't skimp on the power plant. The floats add weight, drag, and getting the plane off the water requires more power. The plane is going to be even more difficult to bank for turns, so give yourself plenty of control throw at max. There is a float flying discussion group as well.

Float flying requires MUCH more refined technique for take off and landing . You cant force the plane into the air, and you can't just drop it down on the water. You also have to make sure you have the floats mounted correctly in relation to the CG of the plane.

Good luck,
Brad