While swimming forward, use a healing treatment ... you stand up, and then start floating across the top of the water like Jesus in the Bible or something. Haha!

This is actually a special case of a larger bug, I think, wherein you can perform certain movements while walking, and your player model freezes in a "stand still" position even though they are moving, so they appear to ice-skate/float forward rather than run or walk. Stopping your movement and restarting causes the character to go back into their animation.

It may only be a graphical bug, but it isn't limited to any one video card.