DIVER EXTRAHEAD to HEAD:
Imagine the problem for Blandford Sub-Aqua. The company used to import two very successful ranges of diving products which did not overlap. Then one of the makes, Mares, now part of the European HTM conglomerate, brought out its own range of computers. And at the same time the rival Suunto computer brand departed from the Blandford stable.
The Suunto Solution was considered one of the industry standards in the dive-computer world, and a huge advance on the first Suunto computer to reach the UK market.
Now the Mares Tutor, augmented by the late-arriving Surveyor, has established itself in the marketplace, while Suunto (now distributed by Suunto Diving UK) has gone on to replace its ageing but ever-successful Solution with the all-singing, all-dancing Vyper.
The Suunto Vyper can be used as an air computer, a nitrox computer or simply in gauge mode to measure and record depth and time (ideal for trimix divers).
The Mares Surveyor until now has been a straight air computer, which is the form in which I tested it, but it is out shortly in nitrox guise and still undercuts the Vyper by almost£50.
DRY-FINGER EXERCISE
There are several similarities between these designs. Both are neat little wrist units which run on user-replaceable batteries. The Vyper uses a lithium one which should last about two years; the Surveyor uses an easily obtainable AAA battery, which needs replacing about every three months.
Both makers have turned to buttons rather than wet-finger contacts to spark the computers into life and extract data between dives, two on the Surveyor and three on the Vyper. Both computers are extremely easy to set. The Vyper has many more options with regard to nitrox settings so there are menus and sub-menus. The third button allows you to backtrack on settings.
Both computers offer a calendar/watch function. I dont expect anyone seriously to use either as an everyday watch but they are useful on a dive trip, when wearing a computer on your wrist between dives looks less silly. The Surveyor can be set for fresh or sea water, whereas the Vyper is fixed for worst-case saltwater conditions.
When I reviewed the Surveyors cheaper sibling, the Tutor, as a straight air computer, I found little to criticise. However, I was using it extensively in tropical waters so never noticed the absence of any screen illumination. But both the Surveyor and Vyper have very effective backlights, operated by one of the buttons and essential when diving in low light conditions - that is, on every UK dive.
You can leave the Surveyor permanently lit during the dive, although this affects battery life, especially if you forget to turn it off when you come up.
HOWLS OF DERISION
Some figures displayed on the Vyper are marginally bigger than those on the Surveyor but I noticed little difference in clarity under water. The Vyper has a graphic to represent nitrogen loading for those who have trouble understanding a decreasing no-stop time.
When I learned to dive, long ago, the poor ignorant foreigners who taught me left me with the habit of always waiting five minutes at 5m before finally ascending.
Back in Britain, this idea was met with howls of derision from BSAC instructors who said it was dangerous to stop, and that we should go directly to the surface.
Then came the BSAC 88 tables, with the 6m stop. People wrote to Diver protesting that it was not possible to stop so shallow!
Thank goodness those days are over. Both these computers encourage you to make a stop between 5m and 3m, even if it has been a no-stop dive. They both count down three minutes at 3m.
Those foreigners who taught me must have known something after all. But then, the Suunto is made in Finland and the Mares comes from Italy.
Both units use algorithms which reflect the latest thinking about decompression and repetitive diving. They both have nine theoretical tissue compartments with half-times from 2.5 to 480 minutes.
The Vypers logbook will remember around 36 hours of diving and the Surveyors about 20 hours. Both feature dive simulation programs and will download on to a home computer, with the appropriate PC interface.
These computers come with straps that are long enough to go round a bulky drysuit wrist. It amazes me that there are still some which do not.
The Surveyor takes into account the increasing rate of pressure changes towards the surface and alters the ascent rate accordingly. This varies from 10m/min at less than 10m to 18m/min at more than 20m. Like previous Suunto computers the Vyper requires one maximum ascent rate from any depth (10m/min) and sounds an alarm if you beat it.
However its clever display indicates ascent rates between 4m/min and 12m/min and you can choose to vary things according to how deep you are.
Anyone can go through the specifications and compare dive computers on paper. I wanted to see how these two instruments compared side by side when used for both no-stop and decompression-stop dives.
The core function of any diving computer is to give you the information that allows you to go under pressure breathing compressed gas and return without injury. So I took these two on a series of 10 dives over four days. Each time they came up with almost identical results! Both were more cautious than the previous generation of computers that sat alongside them on my wrist.
DISCREET TELLING-OFF
The Vyper is ideal for those who want to do more adventurous diving. The Surveyor gives you a discreet telling-off if you do any dive that might be provocative, including venturing beyond 40m, embarking on a series of dives with less than a two-hour surface interval, and deco-stop dives.
This telling-off comes up in the form of a series of asterisks next to the u.b.a. motif. What u.b.a. stands for, I have no idea.
After each dive I had no trouble extracting logbook information from either computer - thanks to their buttons.
The Suunto Vyper gives you everything you want in an air/ nitrox computer except air-integration. It costs £299. If you believe you will never use nitrox, the air Surveyor is a very useful machine for a lot less money -£225. Then again, the Surveyor Nitrox model on its way still costs less than the Vyper, at£250.

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