We flew the Kyosho Pby Catalina last week on our vacation.
Here is a video:

http://media.putfile.com/Kyosho-Pby-...ne-RC-Electric

Setup was modified to have both motors (see above) drawing on one TP 4200 mAh 3s lipo. That lowered the weight and it flew off the water better. Water is sticky and it takes a ton of power to get a seaplane into the air. Once airborne, the Kyosho flew fast, very fast. For a 5 minute flight we used 2400 mAh and ended with an 11.5 pack voltage before the recharge. Props were 9x6 APC e props. This gives only about 1/8" clearance with the fuselage but it was enough. Three bladed props may help but would drain one pack very quickly. I don't see 2-3 minute flights as much fun.