The deep-stops reckoning

Posted 04 July 2026 · Field Note #22

A decompression stop is a deliberate pause on the way up that gives your tissues time to release inert gas before the next drop in pressure. The long-running question is where to spend that time — deep, shallow, or spread between.

For years, bubble-model thinking pushed divers to add stops deep. The logic sounded elegant: pause early, while pressure is still high, and you'd crush tiny bubbles before they had a chance to grow. A whole generation of profiles leaned this way.

Then the US Navy's NEDU study put it to the test. Researchers compared a deep-stop schedule against a shallow-biased one of equal total runtime — same time in the water, just distributed differently. The deep-stop profile produced more decompression sickness, not less.

Why? The physics cuts both ways. Stopping deep does slow bubble growth, but at that depth the surrounding pressure is still high enough that your slow tissues keep on-gassing — soaking up more inert gas — while you hang there waiting. You buy a little bubble control up front and pay for it with a heavier gas load you must clear later, shallower, with less time to do it.

The takeaway most planners now lean on: don't manufacture deep stops for their own sake. Spend your decompression time where it actually clears gas — in the shallows, where the pressure gradient driving gas out of your tissues is steepest.

This is why modern gradient-factor practice tends toward a higher GF-low (less deep-stop emphasis) than the aggressive bubble-model settings of a decade ago. It's also why running the same dive through different models is so instructive — you can see exactly where each one wants you to spend your time.

None of this is settled dogma; decompression is a field of educated bets. But the weight of evidence has shifted firmly away from deep-for-its-own-sake.

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