The first and most important thing to remember when playing water volleyball is that the ball will get heavier. So, preventing it from touching the ground will be much more challenging.
Additionally, the surface of the pool is slippery, so the chances of accidents and injuries are higher. So, you need to be more careful when playing in the pool than on the ground. Finally, the depth of the pool determines how easy or difficult the game is; as such, playing volleyball is much easier in shallow pools than in deep ones.