The Scuba Safety Stop: How Long, How Deep, and Why

Almost every recreational dive ends the same way: the group rises to five metres, someone holds up three fingers, and everyone hangs there watching a countdown. It is the most repeated procedure in sport diving, and one of the least explained. This article covers what the stop is for, where it came from, what the research does and does not show, and how to make one well, including on the dive where your cylinder is nearly empty and the swell is pushing you around.

Last updated 3 November 2026.

What is a safety stop?

A safety stop is a planned pause near the end of the ascent, made in the 3 to 6 m (10 to 20 ft) range, "usually at 5 metres/15 feet for three minutes or longer", in the words of PADI's Open Water Diver Manual.^{[1 ]} You make it on a no-stop dive, one that stayed inside the no-decompression limit, so the tables and the computer would allow you to ascend directly to the surface. The same manual frames the stop as "added conservatism": it "provides extra time for your body to eliminate nitrogen, and it gives you a moment to stabilize and control your ascent rate before continuing to the surface".^{[1 ]}

Dive computers build it in. A Suunto D4i, for example, runs a three-minute countdown for a recommended stop at 3 to 6 m on every dive deeper than 10 m (30 ft).^{[7 ]} Other makes have their own versions; the manual for yours says when it counts one and for how long.

How is a safety stop different from a decompression stop?

The difference is whether the model requires it. On a no-stop dive, the gas your body has absorbed stays under the limit the model allows at the surface. Erik Baker describes these no-decompression limits as "surfacing values only": a no-stop profile is designed so the computed gas loads never exceed them, which is what allows a direct ascent.^{[9 ]} The safety stop adds time on top of that.

Stay longer than the no-stop limit and the model gives you a ceiling, a depth you must not rise above until enough gas has left. The stops that clear it are decompression stops, and they are part of the plan, not margin. Computers show them differently for that reason. When a Suunto adds a mandatory stop, it shows a ceiling and the instruction "NEVER ASCEND ABOVE THE CEILING!"^{[7 ]} If you want the longer story of ceilings and decompression stops, our introduction to decompression starts from zero.

Why do divers make a safety stop?

The stop exists because slowing the ascent was not enough. For decades the US Navy taught a linear ascent of 18 m (60 ft) per minute, a compromise between free-swimming combat divers and helmet divers. The Navy later slowed it to 9 m (30 ft) per minute.^{[3 ,5 ]} When even that did not eliminate decompression sickness, a single brief stop at about 5 m for 3 to 5 minutes was introduced.^{[3 ]} PADI's own history of the stop credits ascent-rate and bubble studies by Andrew Pilmanis in the 1970s and a later Doppler study by Donna Uguccioni, and says PADI's 1988 Recreational Dive Planner brought the stop to a wider audience.^{[2 ]}

Why the shallow end? Because the pressure falls fastest there in relative terms. Rising from 25 m to 20 m takes you from about 3.5 to 3 bar, a drop of one seventh. Rising from 5 m to the surface takes you from about 1.5 to 1 bar, a drop of one third. DAN puts it plainly: safety stops "are a great way to slow and pause your ascent in the shallow depths where the greatest changes in pressure occur".^{[5 ]}

What does the evidence show?

Most of the evidence comes from Doppler ultrasound, which counts gas bubbles in the venous blood after a dive. Such bubbles are common even after ordinary recreational dives. In an earlier field study of 1,418 recreational dives by Marroni and colleagues, 85% of repetitive dives produced detectable bubbles.^{[3 ]}

The clearest test of a shallow stop is the same group's 2004 study: 22 volunteer divers, 181 dives to 25 m (82 ft) for 25 and then 20 minutes, with different ascent rates and stops.^{[3 ]} At a 10 m per minute ascent, the bubble score (one combined score for the dive and the repeat dive, on two grading scales) was:

Adding the shallow stop lowered the score, and adding a deeper stop as well lowered it much further. The same study also tested a very slow linear ascent of 3 m per minute with no stops, and it gave the highest scores of all, 8.78 / 9.97, despite taking eight minutes to reach the surface.^{[3 ]} Crawling up is not the same as stopping. A follow-up study by the same group varied the length of the 6 m stop, from 1 to 5 minutes and up to 10, on the same 25 m dives with a deep stop included. Stretching the shallow stop to 10 minutes did not reduce bubbles any further.^{[4 ]} The ascent rate matters too: DAN reports a 2009 study of 47 recreational divers in which those who ascended at 60 ft per minute showed higher bubble grades than those who ascended at 30.^{[5 ]}

What the evidence does not show

These studies measured bubbles, not decompression sickness. Bubbles are a useful marker: a Norwegian study of 203 air dives found venous bubbles to be a "highly sensitive, although not specific" predictor of decompression problems, meaning many divers with bubbles have no symptoms.^{[6 ]} Decompression sickness after no-stop recreational dives is rare, so a trial large enough to count cases avoided by a three-minute stop would need a very large number of dives. The studies above also used small groups, one depth and one pair of bottom times. The honest summary is that a shallow stop reduces a marker of decompression stress on dives like these. It does not turn a dive past the limits into one within them, and it does not make up for a fast ascent before or after it.

How long should a safety stop be?

Three minutes is the standard teaching, and 3 to 5 minutes is the range most often quoted.^{[1 ,3 ]} Longer does no harm if you have the gas, though in the follow-up study above a 10-minute stop did no better for bubbles than a 5-minute one on those dives.^{[4 ]} Your computer may ask for more: some Suunto models lengthen the stop, or make it mandatory, after you ascend faster than 10 m (33 ft) per minute for more than five seconds.^{[7 ,8 ]}

How deep should a safety stop be?

Usually 5 m (15 ft), anywhere in the 3 to 6 m (10 to 20 ft) range.^{[1 ]} The range is there to be used. In a swell, the deeper end is usually easier to hold still in, because wave motion fades with depth. On a sloping reef or a mooring line, pick the depth where you have a reference to hold.

When is a safety stop required, and when is it optional?

It depends on your agency and your computer, so the rules below are examples, quoted from their sources, not a universal standard. PADI's Open Water Diver Manual says "you should consider it a standard practice on virtually all your dives", and to consider it required if:^{[1 ]}

1. the dive has been to 30 m (100 ft) or deeper;
2. your pressure group at the end of the dive is within three pressure groups of the no-decompression limit on the Recreational Dive Planner; or
3. you reach any limit on the Recreational Dive Planner or your dive computer, which on a computer means it showed zero no-decompression time at any point in the dive.

The same page lists when the stop becomes optional: very low air, assisting another diver, or rising bad weather, when they "make it more important to get to the surface immediately".^{[1 ]} Dive computers add their own rules. A Suunto counts a recommended stop on dives deeper than 10 m and adds a mandatory one after a fast ascent; on some models, skipping the mandatory stop means "the decompression model will penalize your next dive(s)".^{[7 ,8 ]} Other agencies and computers word this differently. Your course manual and your computer's manual are the references that apply to you.

How fast should you ascend to and from the stop?

The US Navy and NOAA use 9 m (30 ft) per minute, and recreational training agencies recommend between 9 and 18 m (30 and 60 ft) per minute.^{[5 ]} Dive computers set their own limit: Suunto's ascent bar goes red above 10 m (33 ft) per minute.^{[8 ]} In practice, the ascent bar on your computer is the instrument to watch, because few divers can judge their rate by feel in midwater.

The stop does not end the ascent. The last 5 m to the surface is still the largest relative drop in pressure of the whole dive, so the same rate applies after the countdown as before it.

How do you hold a safety stop well?

Holding still at 5 m is harder than holding still at 20 m, and most of the reasons are predictable.

Weight for the end of the dive

At the safety stop you are as light as you will be all dive. The cylinder has lost most of its gas: an aluminium 80 holds about 77 cubic feet of air when full (the reason is in our cylinder capacity article), roughly 2.6 kg (5.7 lb) of it, and by a 50 bar (725 psi) reserve about 2 kg (4.4 lb) of that is gone. A wetsuit compressed at depth has expanded again and floats you more. Weight that left you comfortable at the start of the dive can leave you unable to stay down at 5 m with a near-empty cylinder, which is why weighting is usually checked for that moment.

Dive Kit's free Buoyancy calculator in the app adds up your cylinders, suit and gear and checks your weighting at the end of the dive, at a 3 m safety stop with the cylinders at a 50 bar reserve (how it works). The scuba weight calculator on this site does the same sum in a browser. Both give a starting figure. A weight check in the water, near the end of a dive, is what settles it.

Use a reference

PADI's manual puts it simply: "It's easiest to do this holding onto a line or on an ascending slope, but you can also hover in midwater where appropriate."^{[1 ]} A descent line, an anchor line or your own buoy line gives you something to read your depth against. In midwater, your computer's depth and your buddy's position are the reference, so check both often.

Surge and current

In a swell, move to the deeper end of the 3 to 6 m range and avoid fighting every wave with your wing; small breaths and a steady depth average out. In a current with no line, the group usually drifts the stop under a buoy so the boat can follow. If you lose a line in a current, staying with your buddy matters more than staying on the line. Your dive briefing and your training cover the local procedure; follow those.

How much gas does a safety stop use?

Not much, but it has to be in the plan. At 5 m in sea water you breathe at about 1.5 bar. With a surface breathing rate (SRMV) of 20 litres per minute, three minutes there use about 90 litres, roughly 8 bar from an 11.1-litre aluminium 80. In imperial units, 0.7 cubic feet per minute becomes about 3.2 cubic feet, roughly 120 psi from the same cylinder. A cold, tired or anxious diver breathes faster, so allow for more. The breathing-rate terms are explained in SAC, RMV, and SRMV.

The 2006 printing of PADI's manual says to plan the dive "so you can make a safety stop and still reach the surface with 20–40 bar/300–500 psi or more air remaining in your cylinder".^{[1 ]} Dive Kit's gas tools mark a plan that ends under 50 bar (725 psi) in red, whatever reserve rule you set, and the reserve article covers why 50 bar and 500 psi are not the same reserve.

In the app, the Gas Usage tool lets you add the safety stop as its own step, with its own breathing rate, so its gas is counted in the plan (how it works). The free gas consumption calculator on this site runs the same arithmetic for a dive in a browser.

What if you miss or cut short a safety stop?

On a no-stop dive inside the limits, the tables and computers allow a direct ascent at the stated rate, so a missed safety stop is a lost margin, not a missed requirement.^{[1 ,9 ]} There are good reasons to skip one: PADI's own list is very low air, helping another diver, and worsening weather.^{[1 ]}

What happens next depends on your computer. Some treat a skipped mandatory stop as a reason to be more conservative on later dives.^{[8 ]} Read the manual for yours before the trip, not after. A missed decompression stop is a different matter, and your training covers what to do about it.

This article is not medical advice. Symptoms of decompression sickness include unusual fatigue, joint or muscle pain, numbness or tingling, and a blotchy rash. DAN notes they "usually appear within 15 minutes or up to 12 hours after surfacing".^{[11 ]} If you have any symptoms after a dive, contact DAN or the local emergency services rather than waiting to see.

For technical divers: the safety stop and the last deco stop

On a decompression dive, the schedule's last stop, usually at 3 or 6 m, does the job the safety stop does on a recreational dive, and the model sets its length. With Bühlmann and gradient factors, the second number, GF high, is the "surfacing value": it sets how close to the M-value your tissues may be when you arrive.^{[9 ]} Extra minutes added at the last stop work in the same direction as a lower GF high, by lowering the gas load you surface with. A 3 m last stop and a 6 m one also give different schedules depending on your last gas; Same Dive, Different Stops has the numbers.

One caution on the deep-stop result above. Marroni's lowest bubble scores came with an added 15 m stop on a no-stop dive.^{[3 ]} That finding did not carry over to decompression dives: in a 2011 US Navy trial, moving stop time from shallow stops to deeper ones raised the rate of decompression sickness from 3 cases in 192 dives to 11 in 198.^{[10 ]} Unpacking Gradient Factors follows that story in full.

Questions divers ask

Is a safety stop mandatory?

On a no-stop dive it is extra margin, not a stop the model requires, so most agencies recommend it on every dive rather than mandate it. PADI's Open Water Diver Manual treats it as required on dives to 30 m (100 ft) or deeper, when the dive ends within three pressure groups of the no-decompression limit, and when you reach any limit on the table or computer. Some dive computers add a mandatory stop after a fast ascent. A decompression stop is different: that one is required.

How long is a safety stop?

Three minutes is the standard teaching, and 3 to 5 minutes is the range most often quoted. Longer does no harm if you have the gas. In one Doppler study, stretching the 6 m stop from 5 to 10 minutes did not reduce bubbles any further on those dives.

How deep is a safety stop?

Usually 5 m (15 ft), anywhere in the 3 to 6 m (10 to 20 ft) range. Use the deeper end when surface waves make the shallow water hard to hold still in.

Do I need a safety stop on a shallow dive?

PADI calls it standard practice on virtually all dives. Some Suunto computers count a recommended stop on every dive deeper than 10 m (30 ft). On a very shallow dive there is little to do it in, but the stop also gives you a pause to control the last few metres of the ascent, which helps on any dive.

Does the safety stop count as bottom time?

On the PADI Recreational Dive Planner you do not add the safety stop to your bottom time. A dive computer tracks the stop as part of the dive automatically.

What happens if I miss a safety stop?

On a no-stop dive inside the limits, the tables and computers allow a direct ascent at the stated rate, so a missed safety stop is a lost margin rather than a missed requirement. Some computers treat it differently: a Suunto that called a mandatory stop after a fast ascent penalises the next dives if you skip it. Check your computer's manual, follow your training, and if you have any symptoms after a dive, contact DAN or the local emergency services.

Is a safety stop the same as a decompression stop?

No. A decompression stop is required by the model: you have a ceiling, and rising above it before it clears takes you outside the plan. A safety stop is a pause on a dive that never had a ceiling, made because the shallow end of the ascent is where the pressure falls fastest in relative terms.