Surface Swim

[MXGratefulDiver]

I find surface swimming with my face down and my regulator in my mouth to be the easiiest. It might be because whenever I do it that way, my right hand is squeezing the trigger of my Sierra ...

... Bob (Grateful Diver)

 

[highdesert]

I'd say it's largely number 3. Surface vessels (and surfaced divers) create bow waves and wakes, which take huge amounts of energy that cannot be applied to forward motion. I can assure you that a dolphin that can hit 30 knots underwater cannot do so on a surface swim, even though it's required to surface for air, which would make surface swimming more "convenient". Submarines are also much more efficient under water. You might claim that they must produce invisible underwater "bow waves", but the hydrodynamics are different and much more advantageous to the sub when submerged.

 

[highdesert]

Re: My post above ...

"A streamlined body moving in a straight line at a constant speed, deeply immersed ... presents the simplest case of resistance. Since there is no free surface, there is no wave formation and therefore no wave-making resistance."

"A ship moving on the surface of the sea experiences frictional resistance and eddy-making, separation, and viscous pressure drag in the same way as the submerged body. However, the presence of the free surface adds a further component. The movement of the hull through the water creates ... areas of increased pressure at bow and stern and of decreased pressure over the middle part of the length."

"There is greater pressure acting over the bow, as indicated by the usually prominent bow wave build-up, and the pressure increase at the stern, in and just below the free surface, is always less than around a submerged body. The resulting added resistance corresponds to the drain of energy into the wave system, which spreads out astern of the ship and has to be continually recreated."

Chapter 5, Sections 1.4 and 1.5, Principles of Naval Architecture, SNAME Publications.

(SNAME = Society of Naval Architects and Marine Engineers)