I USED TO THINK THAT ALL WATCHES had a certain timeless simplicity to their design. The demands of setting a dozen figures in a circle limited designers in what they could do.
All watches were the same except that some substituted a little gold crown at 12 oclock or perhaps gold for stainless-steel, or diamonds in place of numbers. Then wrist chronometers came along. These had extra dials set within the face: dials for pilots, dials for meteorologists, dials for divers. Watches didn't simply tell the time. They said something about the wearer. And if you couldnt afford a watch and wanted to know the time, you asked a policeman!
Times change. Nowadays you look at your phone, and if thats not handy, theres always your microwave, or your TV or PC.
Thanks to the microchip, everything has a time function now. Watches have become a status symbol rather than a necessity. In fact its become quite posh to have a watch that still works by clockwork.
Most diving computers seem to have a time display now, and its common to see divers between dives wearing their computers like watches. So it was only a matter of time before a diving-computer manufacturer made one in a suitably miniaturised format to win permanent residence on divers wrists, whether they were diving or not.
Suunto brought out the Spider advanced computer watch in 1998, closely followed by the nitrox-capable Stinger and more dainty plastic Mosquito. I am only surprised that Suunto has had the market to itself for so long. Now, all that has changed. Enter the Apeks Pulse and the Mares Nemo.
Apeks Pulse: Resolute in anodised black
Mares Nemo: Named after the Jules Verne character, not the clownfish
Suunto Stinger: Classic Scandinavian knuckle-duster
We decided to compare the three computer-watches and found that they were uncannily similar in what they did and, of course, goodbye hands and dials. All the displays are digital.
For those who think digital watches are naff, the designers at Mares have addressed the problem of style with a sleek shiny watch that no-one would be ashamed to wear, whatever the occasion, digital or not. It looks like a blob of melted steel and glass fused to your wrist. The Mares Nemo was presumably given its name with the captain of the Nautilus in mind, rather than an errant cartoon clownfish looking for its dad.
The Apeks Pulse is Japanese-made, and the Japanese know what a digital watch is meant to look like and are sticking to that. It is resolute in anodised black with a round face set in an oval case in the spirit of the original Cambridge Sinclair digital watch. The same manufacturer makes computers for Dive-Rite and Cressi-sub.
The Finnish-made Suunto Stinger, once considered by me to be ugly, has taken on the role of what we expect a computer-watch to look like. Its the classic Scandinavian knuckle-duster that suits a mans wrist.
That said, it would be presumptuous to say that women are directed towards the plastic Mosquito. Either way, as jewellery, the differences simply come down to a matter of personal taste.
On the surface, each computer-watch displays date and time, and functions as an alarm clock or stopwatch if required. Each has an independently illuminated display and each is set up by the use of four buttons set around the rim.
Under water, each instrument is a full-function decompression computer that can be used with air or nitrox, or in simple gauge mode. Each can be set for use with nitrox mixes between 21 and 50% O2.
What makes the Pulse unique is its ability to program in a second nitrox mix (21-99% O2) so that you can still track your decompression if you switch to breathing a richer nitrox mix during the dive to accelerate the process.
To change mixes, you press one of the buttons and hold it for two seconds. It will not allow you to switch if youre beyond the maximum operating depth of the second mix. If you leave mix 1 set at air, it stays there, but otherwise you need to set the mixes before each dive, and the computer defaults each midnight to worst case (50% O2 / 79% N) scenarios. However, if you have forgotten to set mix 1, it flashes at you at the surface before diving.
The Nemo and Stinger can be set either to air or nitrox but cannot be changed between the two if you are not fully off-gassed. I suggest that if you are nitrox-certified you use them permanently as nitrox computers, with air set as nitrox 21, to avoid being unable to switch during a series of dives.
Both can be set to a ppO2 max. between 1.2 and 1.6 bar, whereas the Pulse is fixed at 1.4bar ppO2 for mix 1 and 1.6 bar ppO2 for mix 2. The Pulse displays the current ppO2 for any given depth. All display OTU tracking when set for nitrox.
The Pulse automatically detects altitude and accounts for it, whereas the others allow you to set it manually. The Nemo and Stinger have three alternative personal safety settings, whereas the Pulse offers only two. All three offer all the bells and whistles when it comes to audible alarms.
We took them diving side by side to try to sort out the differences in the algorithms used. There were no horrible surprises.
The Stinger uses the Wienke/Suunto Reduced Bubble Gradient Model algorithm that takes account of the effect of accumulated silent bubbles for repeat diving, as does the Nemo, which uses a Wienke/Mares version with provision for deepwater stops. The Pulse uses a Swiss algorithm (presumably Buhlmann ZH-L16) modified by Randy Bohrer. The effect was found to be that, under water, the deco information displayed by all three seemed uncannily similar, even with repeat dives in the 30-45m range.
The Apeks Pulse costs £295
The Mares Nemo costs£367.50 in steel or£500 in titanium
The Suunto Stinger costs from£455, according to metal finish and strap supplied
Under water, I found the displayed figures equally easy to read. The actual function titles of the Pulse were tiny and very hard to see at first, but once you get to know the display you will not find this a problem.
The Nemos face has a magnifying effect and is actually clearer to read under water than in air. If anything, the Stinger seemed clearest but thats probably because it was most familiar to me.
My first dive with all three computer-watches involved a wait at the surface. The Pulse appeared to have started diving three minutes before the Stinger and Nemo, which I assume was something to do with the depth at which it is activated into diving mode. It was the only time I noticed this anomaly.
The Nemo displays a deepwater stop but, unlike some other computers, will preview the deep stop predicted.
For this function you push on one of its four buttons during deeper parts of the dive. After a square-profile dive to 33m, and with one minute of no-stop time remaining at that depth, it required me to stop for one minute at 16m during the ascent.
Of course, with multi-level diving things are different. It also takes into account any off-gassing you might have done deeper, so that a forecast deep stop might clear before you get up to it.
Nor do you need to make the deep stop at exactly the depth displayed. For example, after a multi-level dive to 42m, I noted a predicted deep stop at 18m.
However, lingering around in the low 20s, this stop was no longer required by the time I got there and I was back to no-stop diving. Mares appears to have managed to write in deep stops that will accommodate the activities of ordinary leisure divers, and not only those decompressing while ascending a fixed line.

slightly more cautious
I was surprised to find that even after such a dive, closely followed by an almost equally deep one on which the Suunto RGBM algorithm would have kicked in with possibly punitive stops, it was the Pulse that was, if anything, slightly more cautious, with up to a minute or so longer stop-times than the others. However, in practical terms there was little to choose between these three computer-watches.
The Stinger uses a fixed maximum ascent-rate of 10m/min, the Nemo varies between 12 and 10m/min and the Pulse uses a variable ascent-rate of 16, 12 and 8 m/min, according to depth.
All three computers count down a three-minute safety stop in the shallows and this is added to the shallowest deco-stop if needed. The Nemo does this from 5m and the Pulse and Stinger from 6m. The Pulse counts down in minutes and seconds, which is handy once youre accustomed to the tiny figures displayed.
After diving, the Pulse offers three pages of logbook info, whereas, for example, the Stinger offers two plus a re-run of the dive profile. All three can be PC-interfaced.
Like all computers, diving or not, there is an endless list of other functions available but not mentioned here. For example, the Nemos instruction manual is the thickest tome for such a purpose I have seen. Forgive me if I have missed out any feature that might be particularly important to you.
Computer watches are more expensive than their full-size counterparts and none of these have user-replaceable batteries, which adds to the cost of ownership. However they are no less readable than their bigger and cheaper brothers and give as much information as you would demand.
Apart from the obvious advantages of the two-mix capability of the Pulse, I am equally happy to do any regular air or nitrox dive with any of them.
  • Suunto Diving UK 01420 587272, www.suunto.com
  • Mares (Blandford Sub-Aqua) 01923 801572, www.blandfordsubaqua.co.uk
  • Apeks Marine Equipment 01254 692200, www.apeks.co.uk