In 2014, three researchers submitted 43 dive computer models to the same simulated profile in a chamber. At 15 meters, the no-decompression time displayed ranged from 60.0 to 84.3 minutes depending on the device. Same depth, same time, almost 25 minutes difference.
This figure says a lot about the notion of the “most reliable model.” No serious ranking can be established from a web page, and we are not going to pretend otherwise.
This comparison is therefore based on manufacturers’ datasheets, consulted on October 3, 2026, on this 2014 study and on a DAN article dedicated to failures. No device was tested by the editorial team.
Why do two computers not display the same no-decompression time?
Each computer applies a decompression model, often derived from Bühlmann or RGBM, with its own safety settings. The study by Sayer, Azzopardi, and Sieber (2014) notes that no model dominates the market and that several manufacturers modify their algorithms themselves. Hence the clear differences for the same profile.
At 50 meters, the measured times ranged from 8.7 to 15.3 minutes.
The authors also note brand trends, with Mares being rather cautious, followed by Uwatec then Suunto, on the models tested at the time, under controlled chamber conditions and on a single square profile type. These results date from a previous generation of devices and say nothing about current models, but they prove that the gap exists. The name of the algorithm matters less than its setting. A Bühlmann set with tight gradient factors can be more cautious than another computer with factory settings. In short, compare the settings.
But beware of the opposite trap. A computer that grants you more no-decompression minutes simply leaves you less margin, and the dive that follows on the same day inherits this load. Read the manual before the first dive.
Which models to compare and what do the manufacturers say?
Here are six common computers, from entry-level wrist to technical watch. Each line only includes what the manufacturer publishes on its site or in its manual, consulted on October 3, 2026. Prices are those displayed on the American brand sites, in dollars, excluding local taxes and shipping fees, and they vary according to country, reseller, and date.
| Model | Format and screen | Announced algorithm | Announced power | Air integration | Displayed retail price |
|---|---|---|---|---|---|
| Cressi Donatello | Watch, large backlit screen | RGBM Cressi | User-replaceable battery | No | Not displayed |
| Scubapro Luna 2.0 AI | Wrist, black and white LCD | ZH-L16 ADT MB or ZH-L16 with gradient factors | Replaceable CR2450 battery, about 2 years or 300 dives | Yes, transmitter sold separately | $499 |
| Shearwater Peregrine | Wrist, 2.2-inch color LCD | ZHL-16C with gradient factors, VPM and DCIEM optional | Rechargeable battery, about 30 h | No | $580 |
| Shearwater Teric | Watch, 1.39-inch AMOLED | ZHL-16C | Rechargeable, 30 h diving, 50 h watch mode | Yes, with transmitter | $1,199 |
| Shearwater Perdix 2 | Wrist, 2.2-inch LCD | ZHL-16C, VPM and DCIEM optional | Replaceable AA battery, 40 to 100 h depending on battery | Yes, up to 4 transmitters | $1,195 |
| Garmin Descent Mk3 / Mk3i | Watch, touch AMOLED | Bühlmann ZHL-16C | Up to 30 h (43 mm) or 66 h (Mk3i 51 mm) diving, always-on screen | Mk3i only, T2 transmitter | From $1,199.99 at launch (November 2023) |
Regarding gas, there is divergence.
The Donatello manages a single nitrox mix and offers a freediving mode. The Luna 2.0 AI accepts three gases, from nitrox 21 to 100% oxygen. The Peregrine goes up to three nitrox mixes, while the Teric and Perdix 2 open trimix in open circuit and a rebreather mode. And these last two clearly target technical divers. For a recreational diver on air or simple nitrox, these advanced modes remain menu lines.
Each autonomy figure comes from the manufacturer. At Garmin, activating air integration drops the Mk3i 51 mm from 66 to 40 hours, according to the manual. This detail matters on cruises, when charging depends on a shared outlet on the boat.
What criteria to consider according to your level?
For what level? A beginner needs a readable screen, clear alarms, and a simple nitrox mode. A diver preparing for technical diving will look at multigas, the choice of algorithm, and the setting of gradient factors. Between the two, air integration and refilling often make the difference.
Start with readability. Numbers that are too small or weak backlighting quickly become a problem in murky water or at dusk, because you reread the screen more often and longer than at the poolside. Try the device in the store with your mask if you wear a corrective one.
Next comes power.
A user-replaceable battery is found everywhere, whereas a rechargeable battery requires an additional charger and cable in the bag. However, recharging avoids poorly replaced seals after a battery change. No choice wins everywhere. Think about the trip you are preparing, the available outlet, and the number of dives per day. Also note who will do the maintenance.
Air integration displays the pressure of your tank on your wrist, via a transmitter screwed onto the first stage. Convenient, but you add a battery-powered device and a wireless link. Keep an eye on your dive pressure gauge and how to read its data, at least during your first outings.
Trimix and rebreathers, on the other hand, require dedicated training. Our article on trimix diving and its prerequisites recalls the required path before needing them.
What to do if your computer fails during a dive?
In Alert Diver (2010), Robert Rossier recalls the basic rule: if your computer fails during the dive, you stop the dive. You only continue if you have backup instruments and you know your decompression status. Otherwise, ascend slowly and controlled with your buddy.
The same article proposes a simple workaround.
Wear two computers, set the same way and using the same algorithm, on all dives in a series. The second thus keeps the nitrogen history if the first shuts down. The old alternative remains valid for those who still master dive tables and know how to use them without hesitation, with a watch, a depth gauge, and a pressure gauge. Thus, a failure in the middle of a trip does not necessarily cost the rest of the dives. The second device has a cost, to be weighed against a week of lost dives.
If you have to start again with a new device, without history, Rossier advises waiting as before a flight, that is at least 12 hours after a single dive without stops and 18 hours after multiple dives or several days. This pause often costs a day of cruising.
A failure is surprising. If the situation worries you, our guide to managing stress and better reacting in difficult situations details the reflex to stop, breathe, think, act.
How to prepare your computer before the first outing?
Before entering the water, check the charge or battery, the active mode, the oxygen percentage if you dive with nitrox, and the prudence level chosen for the day. Update the firmware. These settings weigh more on your margin than the price of the device.
Yet the computer does not replace the rest of the equipment.
Attach it where you can read it without twisting, left or right wrist, and check that the strap holds on the thick suit you might wear in winter. Test the setting on land. A well-adjusted buoyancy compensator before the dive and a serviced diving regulator count just as much for safety. If you are still hesitating between a watch and a computer, we compare the two in our article on the dive watch and its differences with a computer. Both have their place.
Last point, the briefing. The guide announces a maximum depth and duration, and your computer must stay within this framework, even if it allows you more. The concrete cost of a more permissive device is first paid in safety margin, long before the displayed price.
FAQ
Which dive computer should I choose to start with?
Choose a model with a readable screen, simple air and nitrox modes, and alarms that are easy to understand. Try it out in the store and read the manual before diving. Your instructor can help you set the safety level.
Can two different computers give different no-decompression limits?
Yes. The study by Sayer and colleagues (2014) measured from 60.0 to 84.3 minutes at 15 meters depending on the model, for the same profile. If your buddy wears a different device, the dive group follows the more conservative of the two.
Can you take your dive computer on a plane?
Yes, the device travels with you, but check the manufacturer’s manual for transporting rechargeable batteries. Regarding the body, DAN recommends waiting at least 12 hours before a flight after a single no-decompression dive and 18 hours after multiple dives or multiple days.
What should you do if an alarm goes off during the dive?
Stop, read the screen, and inform your buddy. Most alarms indicate a too rapid ascent rate, maximum depth, or low pressure. Follow the procedures learned in training and, if in doubt, end the dive.
Sources
- Decompression management by 43 models of dive computer: single square-wave exposures to between 15 and 50 metres’ depth (Martin D. J. Sayer, Elaine Azzopardi, Arne Sieber, Diving and Hyperbaric Medicine, 2014)
- Your Computer Fails: Now What? (Robert N. Rossier, Divers Alert Network, Alert Diver, 2010)
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