Do you mean the character in the ring slowed down, or the performance of the game? Currently, the procedurally generated water mesh has waves which update each frame, and the floating ring is physically effected by these waves. This means, if a wave is behind you, it will carry you forwards and when your moving into a wave in front you will slow down. Reworking the water functionality is near the top of my list of things to fix, so it will be simpler in future builds.