[aj906]

Originally Posted by Sailor Steve

Actually drag is worse on the surface due to wave resistance. As the hull moves through the water waves build up along the waterline, and the waves create more drag.
http://www.mecaflux.com/en/ship%20Hydrodynamics.htm

But at 4 knots (as your latter post implies) this will not be a problem. And, with batteries engaged, it is not like you would want to do much more than about that for the sake of economical cruising. Also, if it is such an issue - and I'm not for one minute questioning you - why would it be a viable option related by veterans? Perhaps their recollections refer to mill-pond conditions only and I missed that implication