 Advantages are reduced overall decompression time and for some versions, easy estimation of decompression by the use of a simple rule-based procedure which can be done underwater by the diver.It requires the use of specific gas mixtures for given depth ranges.The advantages claimed are flexibility in that if the depth is not known accurately, the schedule can be adjusted during the dive to allow for the actual depth, and that it allows deep dives without the use of an expensive trimix dive computer.