Have seen this repeated many times at a nudist resort. Usually it's just penetration without much movement. Had a guy standing by my wife in the pool. We were in water deep enough to cover his dick but her tits were out, nipples erect! He soon sported a huge hardon, much bigger than mine! He would occasionally reach his hand under water and jerk his dick a few pumps and stop. Very hot to watch him as she displayed her tits to him!~~~Aaron