The guy who mentioned the benefits of orange peel surface to reduce friction is ALMOST right, but not quite. America's Cup boats - those that you see on ESPN every 4 years - have been using wnat is called 'Riblets' for the past 20 years ago or so on their hulls - below the water line. These riblets are very small grooves that run lengthwise to the boat and reduce drag. The grooves are not actually part of the hull, but are applied to the surface of the hull much as a decal is applied. The depth, width and spacing of the grooves was developed with millions of $ in research and developmental testing.

I doubt that there would be any positive or negative impact on the operation of a RC float plane, and the down side is that if the exact right groove depth, width, spacing and orientation to the floats of the grooves wasn't used the floats would be less able to get up on step and the speed could be reduced.