You might even take into account the fact that when beaching, the hull will take a beating also. If you fly around gravel or a rough beach, fiberglass the forward part of the hull where it will take the most abuse. Use 3/4 ounce cloth with 50/50 epoxy and alcohol.

I thought you were more concerned about preparation of the wing and hull prior to flight. Floats or flying boats, they all need to be sealed the best you possibly can. Water WILL get in, it's just a matter of how much and when.

" Is the rest of the airplane covered or protected in a special way?"

Just make sure it's sealed so water can't get in the wing and loosen the covering or change the CG.