IIRC mythbusters used a medal winning swimmer and he couldn't perform. His body was attuned to swimming in water and he was messing up on his strokes (from what

IIRC mythbusters used a medal winning swimmer and he couldn't perform. His body was attuned to swimming in water and he was messing up on his strokes (from what it looked like, he was taking longer to do a stroke in the more viscous liquids but he was going further with each stroke).