A stabilising waistcoat or stab is needed to balance the diver in the water.
Stabilising jackets can be used at any depth. A wide range of waistcoats are available, with all the options available.
From the simple 'club' diving stab to the model incorporating removable lead pockets and a 'tec' type harness, they all have an inflator.
The stabiliser waistcoat can be emptied using high and low quick-drain valves, as well as the inflator or a quick-drain valve at the top of the corrugated hose known as the Fenstop.
Note that it is not necessary to look for large volumes of stabiliser waistcoat if you are diving with a single tank, for example. The greater the volume, the more the hydrodynamics will be reduced.
Finally, it's a good idea to choose a product that's easy to find parts for.