A review of those floats that I saw said that as long as all you want them for is to stop the drone sinking … then fine. But keeping it dry? Unlikely.
When it’s floating on the water, it’s very top-heavy, and it will only handle pond-like ripples. Anything more, and it will flip inverted.
Also - since the chances are these will only be needed in the case of an auto-land, you probably have already lost control … and the auto-land may not slow down over water as it nears the surface, since the visual system really needs some detail - so you are reliant on the ultrasonic sensors, and the reflection from water is a bit iffy.
As a result, a standard descent speed auto-“landing”, will (a) probably dunk the drone, and (b) cause it to flip … even on a smooth surface.