Multilevel Dive

A dive planned in progressively shallower stages, gaining more total bottom time than a square profile at the deepest depth would allow.

A multilevel dive is planned as a sequence of depth stages, deepest first, each shallower than the last. Because nitrogen uptake slows as you move shallower, spending the later part of the dive at reduced depth stretches your no-decompression time well beyond what a square profile at maximum depth would permit. This is the natural shape of most reef dives: drop to the deepest point of the plan, then work gradually up the slope or wall toward the safety stop.

Dive computers made multilevel diving practical by recalculating your remaining no-stop time continuously as depth changes, crediting the shallow segments in real time. Before computers, tools like the PADI Wheel approximated the same idea with tables. The rule that makes it work safely is always deepest first: starting shallow and finishing deep, or repeatedly bouncing between depths in a sawtooth, loads tissues in ways the models handle poorly.

When planning a multilevel dive, pick two or three target depths with rough times at each, confirm gas will not be the limiting factor, and agree the levels with your buddy. The profile your computer records afterward shows how closely the dive matched the plan. If the reef tempts you back down after you have moved shallow, resist it: the credit your computer gave you assumed you stayed up.