With practice, divers learn to minimize this problem, starting by minimizing the volume of gas required in their BC's. This is done by using the minimum weighting needed for their equipment, which keeps the volume of the gas in the BC as small as possible at the beginning of a dive. Just enough gas will be added tp the BC to compensate for the slow loss of weight as the dive progresses, as a result of gas use, which will vary according to the dive, but is limited by the cylinder contents. (in practice, for a recreational diver, this will be about per cylinder).