The safety stop as a skill: plan your gas, hover cleanly at 3 to 5 metres and the honest answer on what the stop really achieves. Practice with an instructor.
What does the safety stop really achieve, and how do you do it right? The honest answer: it is a five-minute pause at 3 to 5 metres just before surfacing, a widespread practice [1]. Its benefit is plausible, but according to a current review on decompression illness it is not supported by definitive studies [1]. Your dive computer does not demand it on a dive within no-decompression limits [1]. You do it as an additional buffer.
There are reasons it is taken seriously anyway. In a case-control study among divers in Okinawa (94 with decompression sickness, 175 healthy divers), safety stops appeared as a protective factor, alongside drinking before the dive and nitrox [2]. And a review of injury research calls for continued promotion of safety stops and conservative ascent rates [4]. On top of that, ascent speed counts: divers who ascended after the same 35-metre dive (with decompression stops) at 17 instead of 9 metres per minute formed more gas bubbles in their blood [3].
Without the skill, though, the stop stays theory: if you cannot stand still at 4 metres, you swing between 2 and 6 metres. This guide shows you how to practice the stop as a skill. It does not replace an instructor.
Prerequisites (training practice):
The stop costs five minutes of air. Plan it before the dive: start the ascent so that you reach the stop with enough reserve and still have enough left at the top. Insufficient gas was the most frequent trigger (41 percent) in an analysis of 947 fatal diving accidents [5]. If your gas runs low, air takes priority over the stop. Agree with your instructor in the briefing how you handle this.
Milestone: before the dive you can say out loud at which cylinder pressure you begin the ascent.
Ascend slowly and in control. Release air from the jacket during the ascent so it does not expand and speed you up. Keep an eye on the computer.
Milestone: you reach stop depth without overshooting upward.
The stop is held at 3 to 5 metres [1]. What you learned in the hovering guide applies here: horizontal, calm breathing, no hands, no fins. If there is a line, hold it only loosely. Pressure changes the most in the top ten metres, so every bit of calm pays off here [6].
Milestone: for five minutes you hold the depth without swinging more than half a metre.
The computer usually displays the stop. Wait the full five minutes [1]. Use them: read your cylinder pressure, watch your surroundings, check on your buddy.
Milestone: you do not end the stop early just because you are bored or cold.
After the stop you keep ascending slowly, the last metres especially calmly. Only inflate the jacket at the surface.
Milestone: you arrive at the surface in control and without hurry.
Use the stop as a quality test for your hovering. If you stand five minutes at 4 metres without hands, without kicking, without inflating your jacket, your hover is real, not luck. The stop is the only exam every dive brings along for free. And look at your cylinder pressure at the end of the stop: over many dives you learn your consumption.
The benefit is plausible, but not definitively proven [1]. Studies and injury research do speak in its favour [2][4]. On a dive within no-decompression limits the computer does not require it. Do it anyway if your gas allows.
Usually five minutes at 3 to 5 metres, right before surfacing [1]. That is roughly the time you need for a coffee. Exact rules depend on your training and your computer.
Discuss it in the briefing with your instructor. Air takes priority; insufficient gas was the most frequent trigger in fatal accidents (41 percent) [5]. So plan the stop into your gas from the start.
Because speed creates bubbles. In a study of 50 divers, more gas bubbles formed in the blood at 17 instead of 9 metres per minute [3]. Your stop and a slow ascent belong together.
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