Though the whole point of volleyball is to get the ball over the net and into the opponent's court, there are occasions when a player may need to reach or step under the net to save a point. The International Federation of Volleyball has very specific rules about going under the net. If you're used to beach volleyball rules, there are some important differences between the two sports.
Penetration Under the Net
The short answer to whether you can go under the net in indoor volleyball is yes, but there are considerations. For example, you may penetrate into your opponent's space provided you don't interfere with play. This means you can't make contact with an opponent or get in the way of an opponent who is getting into position to make a play on the ball or getting set to play defense.
Hands and Feet Only
The International Federation of Volleyball allows a player to reach under the net into the opponent's area with the hands and feet only. Any other body parts are prohibited. In addition, some part the penetrating hand or foot must be in contact with the center line or be directly above it.
Penalties for Going Under the Net
If a player on the serving team goes under the net in violation of the rules, his team loses the serve. If a player on the receiving team commits an under-the-net violation, his team loses the point. A player may enter the opponent's area after the ball goes out of play. However, all players must be completely on their own side of the center line to start each point.
Beach Volleyball Differences
Now that you understand the rules for going under the net in indoor volleyball, remember that beach volleyball follows slightly different regulations. For example, in beach volleyball a player may go completely under the net into an opponent's side and hit the ball back under the net, provided her team still has enough contacts left to play the point. But as with indoor volleyball, a player cannot interfere with the opposing players if she goes under the net.