Diving weighting systems are a way for scuba divers to stay underwater for a long time. They help you to stay underwater without having to fight against the rising force of the bubbles created by the air released from your scuba tank.
The system consists of different kinds of weights that you put on your body like a vest. The weights make you heavier, so that when you are underwater, the extra weight counteracts the upward force of the air bubbles. That way you don't float upward, and you can stay underwater longer.