Deco Stop (Decompression Stop)

A mandatory pause at a specific depth during ascent, required to off-gas nitrogen safely after a dive that exceeded no-decompression limits.

A deco stop is a mandatory pause at a planned depth during your ascent. Once a dive exceeds its no-decompression limit, you can no longer swim straight to the surface: your tissues carry enough dissolved inert gas that surfacing directly would likely cause decompression sickness. The stops, typically in 3 m increments starting from the deepest required stop, hold you under pressure long enough for gas to leave your body at a safe rate.

Your dive computer or dive tables calculate stop depths and times from your depth and time profile and the gas you are breathing. Missing or shortening a required stop is called omitted decompression and is a genuine emergency protocol situation. Technical divers plan decompression deliberately, often switching to a high-oxygen deco gas at the stops to speed up off-gassing, and carry redundant gas so they can always complete the schedule.

For recreational divers the key point is the difference from a safety stop: a safety stop at 5 m/15 ft for 3 minutes is optional insurance, while a deco stop is an obligation created by your dive profile. Recreational training is designed to keep you inside no-stop limits so deco stops never become necessary. Understanding deco stops is still worthwhile, because an accidental overstay can put one on your computer.