If you move in any direction, move the camera sharply about 90 to 180 degrees, then let go of the button, your character will stand like he is on the ground then revert to his standard underwater movements after about .5 seconds.

Something minor as well...if you move diagonally in any direction while underwater and move in the opposite direction you get some weird position change animations. I can understand the delay in repositioning yourself to swim in the opposite direction but it's like the game detects you moving left or right with his arm extended then continues to swim diagonally.