Comments on floats with a low-wing plane:

The arrangement works fine.
Relative advantages: Low-wingers tend to be more stable than high-wing planes when taxiing in windy conditions. There's not as big a problem of the wind getting under the upwind wing and flipping the plane over. The low wing plane cannot tip as far before the wingtip hits the water, which stops it from tipping more. The low-wing plane also generally has less dihedral than a high-winger so less wind gets under the upwind wing for that reason, too. Several guys in my club fly Astro-Hogs on floats, and they're super.

Relative disadvantages:
1.The wing usually has to be installed/removed through a birdcage formed by the float-mounting struts, so it's a little tedious to attach/detach the wing & servo wires.
Japanese pattern floatplanes have the floats mounted to the wings and not the fuselage, so removing the wing is the same as if the plane had wheels.

2.When a low-wing plane DOES blow over, the fuselage gets more water in it. High wingers tend to float on the wing keeping the interior of the fuselage dryer. Low-wingers float on the wing, too, after the fuselage fills up with water.