Wow! I surfed the links from here to happen across a reversing propellers twin 914 turbos air cam video. Wow! Wouldn't that simplify docking or any other water 'taxi' maneuver. For those who are not float fliers, the wind and water currents can be the biggest challenge of the flight when attempting to dock with no unintentional metal or paint modifications to the floats.
I want one (for what that is worth...

....)
lc
It is certainly NOT a traditional looking back country plane, but I think it would work well when you solve the rocks/props issue.