Dive Profile

The depth-versus-time record of a dive, showing descent, bottom phase, ascent, and stops; the shape that decompression calculations are based on.

A dive profile is your dive drawn as depth against time: the descent, the time spent at each depth, the ascent, and any safety or decompression stops. It is the fundamental object in decompression theory, because how much inert gas you absorb and release depends entirely on this shape. Two dives with the same maximum depth and total time can carry very different decompression obligations if one is a square profile and the other spends most of its time shallow.

Profile shape has its own vocabulary. A square profile drops to depth and stays there, typical of wreck dives. A multilevel profile steps progressively shallower, the natural shape of a reef slope, and yields more no-stop time. A sawtooth profile, repeatedly going up and down, is discouraged because repeated pressure swings encourage bubble formation. Reverse profiles, diving deeper on the second dive than the first, were long forbidden and are now merely advised against for large depth differences.

Every dive computer records your profile at fine intervals, and reviewing the downloaded curve in your logbook shows things memory misses: a fast ascent, a sawtooth section, or how long you really spent at depth. Comparing profiles across similar dives also reveals habits, like a tendency to creep deeper than planned mid-dive, that are hard to notice in the moment and easy to correct once seen.