Originally Posted by mad_machine
why do they let the props hang half out of the water? They would be more efficent if they were not thrashing the water like that
Actually, surface piercing drives as they are known can be very efficient. The shaft of a conventional prop has a lot of drag. Get the shaft out of the water flow and make the props large enough for 1/2 to do the job and there can be significant gains. The thrashing is visible but may not be causing as much drag as the prop shafts would.