THERE WAS A TIME when the first thing a newly qualified diver did was to go and buy a big shiny knife and a chunky looking divers watch.
Today, knives are smaller and diving computers are largely superseding watches. The compromise on the latter is the possibility of buying a computer that doubles as a watch, and nearly all the major diving computer makers can offer at least one.
This means four manufacturers: in Europe, Suunto and a Mares sub-contractor in Switzerland; in Japan Seiko (with products under the Apeks, Cressi, Mares and Scubapro brands sharing similar LCD displays); and, in the USA, Pelagic, a company associated with Oceanic.
Their products are all set up using four buttons, though these are sometimes less than intuitive in function, so dont think they are all the same.
All are calendar chronometers and, in diving mode, are suitable for use with nitrox, though some have anair-only setting left over from when nitrox was still considered by some a devil gas. We suggest that you put these in nitrox mode and set 21% when using air.
Dual-time mode allows you to keep track of time at home while in a different time-zone.
Every computer here has bar-graphs to indicate nitrogen and oxygen loading.
Each has a logbook and history mode, and a PC interface available.
The Suuntos are manually set for diving at altitude; the others automatically sense ambient air pressure.
Every unit is powered by small lithium batteries. The Japanese-made computers can be set manually for fresh or salt water for accurate depth displays, and this does not affect deco or no-stop time calculations.
The Japanese-made computers also tend to default to a worst case 99% O2 overnight. This can catch you out on a dive at first light, should you forget to reset them!

hspace=4 Made in Japan, this computer-watch looks as if it is made of metal, but in fact it is a very lightweight chromed-finish plastic (or in matte black).
Its manual doubles as a useful aid to language students but, like others from the Far East, was difficult to follow in the English version.
A call to the UK Mares representative unlocked the secrets of setting it up.
The Nemo Sport can be set for nitrox up to 99% O2, with a choice of two safety factors, and sampling rates of every 15 or 30sec. It displays a three-minute safety stop at 6m during an ascent. This is probably the best-value computer watch available.

OCEANIC GEO £267(with rubber strap)
hspace=4 This is a desirable-looking item available in four colourways, with a very legible display and, uniquely, a user-replaceable battery. Its just a pity it sent us into paroxysms of frustration during the setting-up, simply because the buttons didnt always seem to do what the instruction booklet promised.
The Geo comes with a long extension strap that indicates that the manufacturer is in tune with the needs of divers.
It uses a Rogers/Powell DSAT algorithm that is less familiar than those used in other computer-watches.
It can be set for use with nitrox mixes up to 50% O2, with a highest ppO2 ceiling of 1.6 bar. It has a safety-stop adjustable for time and depth and a choice of personal safety levels. Maximum ascent rate varies according to depth, with an automatic prompt.
You can opt to switch the Geo on manually instead of using automatic water activation. An O2 toxicity warning and nitrogen loading graphic are included in the alternating displays, operated by push-button while diving. As well as nitrox and air, the unit has gauge and freediving modes.

hspace=4 I suspect that this is made in Switzerland for Mares, although the stated country of origin is Italy. It has a feeling of quality derived from its weightier metal construction.
It would have been easy to set up if it hadnt been for its sticking buttons, 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 20sec in nitrox mode or every 4sec when set for freediving.
Its maximum ascent-rate indicator varies between 12m/min and 3m/min according to the actual depth, and the Nemo Excel can be set for a choice of maximum ppO2 between 1.2 and 1.6 bar.
A 3min safety stop is indicated as soon as the diver returns to 6m.

hspace=4 While they were making a computer-watch for Apeks in the UK, the Japanese seemed to have cracked out an almost identical one, save perhaps for a sexier casing, for Cressi in Italy.
It is said to have a unique Buhlmann algorithm, redesigned by Randy Bohrer to make it suitable for a more sophisticated RGBM program. It has freediving and gauge modes too.
Unfortunately, in its latest incarnation it was so new that we couldnt get hold of one to use under water alongside the others here.

SUUNTO D4 £295
hspace=4 Intended to be as useful for free-divers as for scuba divers, the D4 replaces both the D3 dive timer and Mosquito computer-watch, with sampling rates adjustable between every single second, 10, 20, 30sec or every minute (as with its more expensive D-series siblings).
In free-diving mode, it is also programmed to capture depth readings three times a second for accurate maximum- depth measurements.
The unit is made from a mixture of metal and composite plastic, and dovetails nicely with the rest of the all-metal D-series Suunto computers with its Suunto/Wienke RGBM50 or RGBM100, and iterative deep-stop option interchangeable with automatic safety-stop display.
The D4 can be set with any nitrox mix up to 50% O2. It has a graphic that indicates ascent rate, and another that indicates consumed bottom time (or decreasing no-stop time).

hspace=4 Its surprising that, despite its ownership of the Swiss computer giant Uwatec, Scubapro outsources its computer-watch to Japan.
In common with its siblings bearing other branding, the Xtender can be set for nitrox up to 99% O2 with a choice of two safety factors and two sampling rates (every 15 or 30sec) and it uses acoustic alarms to indicate warnings of such things as exceeded PO2, no-stop times exceeded or an excessive ascent-rate. It comes in gentlemanly black or in a choice of two pastel shades designed to suit a woman better if worn as a watch.

hspace=4 Unique among the Seiko-made computer-watches illustrated here, this one allows users to switch nitrox mixes during a dive so you can carry two gases and speed up decompression. The first mix can be up to 50% O2, whereas the second can accommodate nitrox 99.
The sampling rate can be set at either 15 or 30sec intervals. There is a choice of two safety factors, allowing the degree of caution in deco calculations to be adjusted.
Two alternating displays accessed by pushing a button can be seen under water. There are warnings for exceeded ppO2, deco-stop violations, oxygen toxicity and being out of range. A 3min safety stop is displayed on ascent to 6m.
In Gauge mode, the Pulse becomes a basic depth-gauge and timer. Its strap is long enough to go round the wrist of a drysuit but may become inconvenient on a day-to-day basis.

SUUNTO STINGER £350 (with rubber strap)
hspace=4 Derived from the original computer watch, the Suunto Spyder, the stainless-steel Stinger is a firm favourite with divers and still available despite the advent of the new D-range.
It is intuitive to set up and can work with mixes up from air to nitrox 50. It has the loudest and hence most useful alarm for surface use.
It comes with 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, which kicks in to allow extra caution on second and further repetitive dives.

SUUNTO D6 £470 (with rubber strap)
hspace=4 The nicest looking of all of the digital computer-watches illustrated here, the D6 has
a stainless-steel case with a rubber strap (and extension) or a stainless-steel bracelet.
Like all the D-series computer watches, it is quite intuitive to set up, although the audible alarms are rather muted.
Dont expect it to wake you for that early-morning dive!
Set in the appropriate nitrox mode rather than air, the D6 can be set for two mixes of nitrox for gas-switching on a dive; and can be set to encompass iterative deep-stops or a 3min safety stop that is automatically displayed at 5m.
Like other D-range computers, this one uses a unique Suunto/Wienke Reduced Gradient Bubble Model (RGBM) 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 bar, with a display for actual ppO2 due to depth up to 3 bar) and there are three personal adjustments for caution. Otherwise it can be set to gauge mode for use as a depth-gauge and timer. Like the D9, it has a unique-to-Suunto built-in electronic digital compass.

SUUNTO D9 £995 (with rubber strap + transmitter)
hspace=4 With all the functions of the D6 and more, the chunkier and clunkier D9 is constructed from matte-finish titanium and has the option of a matching user-changeable titanium strap for dress use to replace the extendable rubber one.
The D9 can be set for up to three different nitrox mixes per dive and, uniquely, it is integrated via a transmitter with the gas of the primary supply, providing a prognosis of how long your gas supply will last based on your usage prior to that, your depth and the remaining pressure in your tank.
The D9 displays tank pressure in bar, too.
It cant do this all on one display, so it always 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 an automatic safety-stop display, and uses the Suunto/Wienke RGBM algorithm. Like the D4 and D6, the D9 has a very nice graphic profile of each dive stored alongside other details in its logbook memory. Together with its electronic compass, it provides all the information a diver needs in one compact unit.