Dive Computer Watches

While some divers still like to sport big, expensive dive watches, diving computers are largely superseding watches. It’s possible, however, to buy a diving computer that doubles as a watch, and although the digital face is a bit passé for the classy dresser, some have casings and straps suitable for casual wear.

Only four computer manufacturers make dive computer watches: Suunto, a subcontractor of Mares in Switzerland, Seiko in Japan, and a company that is part of Oceanic. All are calendar chronometers and allow you to keep track of time at home when in a different geographic time zone. In diving mode, they are suitable for use with Nitrox, although some have an “air-only” setting left over from the days when some retailers thought Nitrox to be a “devil gas” (put them in Nitrox mode and set 21 percent when using air).

Every computer here has a bar graph to indicate nitrogen loading and another to indicate oxygen loading. All feature a log book and history mode, employ small lithium batteries, and have a PC interface available. The Suuntos are manually set for diving at altitude, whereas the others automatically sense ambient air pressure. The Japanese-made computers can be set manually for fresh or saltwater for accurate depth displays, although this does not affect decompression or no-stop time calculations. They tend to default to a worst-case scenario of 99 percent O2 overnight, so this can catch you out on a dive at first light if you don’t remember to reset.

Here are the ones I tested, from least expensive to priciest (all prices are list prices).

Oceanic Geo. Very popular with American leisure divers, this desirable-looking item is available in four different colors with a legible display and a user-replaceable battery. It sent me into paroxysms of frustration during the setting-up process because the buttons did not always do what the instruction booklet promised. It uses a Rogers/Powell DSAT algorithm that may show quite different deco and no-stop times than those used in the other computer watches. It can be set for uNitrox mixes up to 50 percent oxygen, and has a safety-stop adjustable for time and depth, plus a choice of personal safety levels. Its maximum ascent rate varies according to depth, with an automatic prompt. An oxygen toxicity warning and nitrogen loading graphic are included in the alternate displays operated by push-button. Besides Nitrox and Air, it has Gauge and Free-diving modes. The battery is easy to change. I liked the display but not the fact that you need to push buttons to see all the information during a dive. $350; www.oceanicworldwide.com.

Mares Nemo Sport. Made in Japan, this looks like it is made of metal but is actually a lightweight chromed-finish plastic (it also comes in matte black). It was a pity that, like the other computer watches from the Far East, its manual was difficult to follow. A call to the Mares representative unlocked the secrets of setting it up. It can be set for Nitrox up to 99 percent O2, with a choice of two safety factors, and sampling rates of every 15 or 30 seconds. It displays a three-minute safety stop at 20 feet during an ascent. Changing the battery involves four screws, so that job might be best left to your dealer. It is probably the best-valued computer watch available, although it feels cheap. $450; www.mares.com.

Apeks Pulse. Unique among the Seiko-made computer watches tested here, the Pulse allows you to switch Nitrox mixes during a dive so you can carry two gases and speed up decompression. The sampling rate can be adjusted to either 15- or 30-secondintervals. You adjust the degree of caution in the deco calculations. There are warnings for such things as exceeded ppO2, deco-stop violations, oxygen toxicity and out-of-range. A safety stop of three minutes is displayed once the diver ascends to 20 feet. In Gauge mode it becomes a basic depth gauge and timer. The battery is not user-replaceable. It’s the least expensive way for a twin-tank diver to get a computer watch that will calculate accelerated deco with a second richer mix of Nitrox. $504; www.apeks.co.uk.

Mares Nemo Excel. It has a feeling of quality derived from its weightier metal construction. If it hadn’t been for sticking buttons, it would have been easy to set up because it was quite intuitive to understand. It uses the Mares/Wienke RGBM algorithm that accounts for the possible effects of repeat diving, and has a sampling rate of every 20 seconds when in Nitrox mode or every four seconds when set for free-diving. Its maximum ascent-rate indicator varies between 40 feet per minute and 10 feet per minute, according to the actual depth. The Nemo Excel can be set for a choice of maximum ppO2 between 1.2 and 1.6 bar. A safety stop of three minutes is indicated as soon as the diver returns to 20 feet. The battery can be changed by the user but involves removing four small screws. The modern Italian case design was a little too avant-garde for my taste. $600; www.mares.com.

Suunto D4. Intended to be just as useful for freedivers as for scuba divers, the D4 has sampling rates adjustable between every single second, 10, 20, 30 seconds or every minute. In freediving mode, it also programmed to capture depth readings three times a second. It is made from a mixture of metal and composite plastic and uses the Suunto/Wienke RGBM50 or RGBM100. The iterative deep-stop option is interchangeable with an automatic safety-stop display. It can be set with any Nitrox mix up to 50 percent O2. It has a graphic that indicates ascent rate and another that indicates consumed bottom time (or decreasing no-stop time). Like the Mosquito it replaces, the D4 employs a Suunto user-installed battery kit. It looks good but feels a lot cheaper than the other Suunto computer watches. However, it is easily the best option if you are into freediving. $649; www.suunto.com/diving.

Suunto Stinger. Derived from the original computer watch, the Suunto Spyder, the stainless-steel Stinger is a firm favorite with divers. It is intuitive to set up and can work with mixes up to Nitrox50. It has the loudest alarm for surface use, and comes with either a useful strap extension or a stainless-steel bracelet that extends itself to go over a wetsuit sleeve. Popular with many technical divers as a gauge, in free-diving mode it displays only depth and duration together with water temperature, and makes no deco calculations. It employs the original Suunto/Wienke RGBM100 algorithm that kicks in to provide extra caution for second and further repetitive dives. Owners are denied the chance to change the battery themselves. It’s an all-time classic design, although it’s starting to look a bit dated. $830 (with rubber strap option); www.suunto.com/diving.

Suunto D6. The nicest looking of all the digital computer watches tested here, it has a stainless-steel case with a rubber strap or a stainless-steel bracelet. It is quite intuitive to set up, although the audible alarms are rather muted, so don’t expect this to wake you for that early morning dive. It can be set for two mixes of Nitrox for gas-switching during a dive and can be set to encompass iterative deep-stops or a clearly displayed three-minute safety stop that is automatically displayed at 15 feet. The D6 uses a unique Suunto/Wienke algorithm that can be set from two versions and takes into account repetitive dives. You can set your own limit for ppO2 (from 1.2 to 1.6 bars with a display for actual ppO2 due to depth up to 3.0 bars) and there are three possible personal adjustments for caution. Otherwise, it can be set to gauge mode for use as a depth gauge and timer. It also has a unique-to-Suunto built-in electronic digital compass. Only an expert can change the battery. $885; www.suunto.com/diving.

Suunto D9. With all the functions of the D6 and more, the more chunky and clunky D9 is constructed from matte-finish titanium and has the option of a matching user-changeable titanium strap for dress use. It can be set for up to three different Nitrox mixes per dive and is uniquely integrated via a transmitter with the gas of the primary supply, thereby giving a prognosis of how long your gas supply will last based on your usage prior to that, the depth you’re at and the remaining pressure in your tank. The D9 also displays tank pressure. It can’t do this all on one display, so it offers the most crucial-at-the-time information first and you can get the rest by pressing a button. It offers deep stops as an alternative to the automatic Safety Stop display and uses the Suunto/Wienke RGBM algorithm. In common with the D4 and D6, the D9 has a nice graphic profile of each dive stored alongside other details in its logbook memory. Together with its electronic compass, it gives all the information a diver needs in one single compact unit. If cost is no object, it’s obviously the best option as a dive computer. No battery change by the user is possible with the wrist unit, although the tank pressure transmitter does allow it. $1,925 (with rubber strap option and transmitter); www.suunto.com/diving.

Bottom line: Because the Mares and Suunto computers use a Wienke RGBM algorithm very similar to that in the Seikomade computers, there is little to choose between them when it comes to core function as diving computers. The Oceanic uses an algorithm that has proved to be very popular. The Apeks allows gas switching, as do the more expensive D6 and D9. When it comes to choosing what’s right for you, it merely comes down to the dive computer’s appearance as a watch. The D6 is easily the winner, unless you prefer the styling of the Nemo Excel. The others look more Swatch than Rolex.

John Bantin is the technical editor for DIVER magazine in the United Kingdom and a professional underwater photographer.