Well... According to aquaticfrogs.tripod.com that could be normal. But since he isn't swimming normally, it prolly mweans something is wrong, but this could point to any number of problems.
Firstly I recommend asking the people at Froggy Friends on Yahoo Groups, they know quite a bit more than I do, but here's a link to illnesses:

http://clawedfrogs.tripod.com/id20.html