Virtually any plane can be converted to a float plane. Planes I have flown on water include multiple Balsa USA Northstars, Balsa USA Stingray, Midwest 80" Citabria and Midwest 80" Extra 300XS. All you need to do is make up some floats that are appropriate for the size of your plane. For my bigger ones the floats end up being about the same size as a .40 - .60 size fuselage!