For many years, technical divers on deeper dives have added deep safety stops to their dives. Initially these stop strategies were used in search of additional safety when conventional dive tables were applied at extreme depths and exposures. This wasn't pure guesswork but based on a theory being developed by a fish collector called Richard Pyle. He observed that when he brought up fish, destined for the aquarium trade, from deep depths too quickly, they suffered a kind of embolism. However, if he brought them up slowly, they didn't. These stops are now known as 'Pyle stops', and deep divers now apply these stops as a method of decompressing. Suunto has adopted a similar model in its new range of computers, namely the Vytec DS (deep stop) and D6 (smaller brother of the D9).

Before the dive, the diver selects the length of the deep stops - either one or two minutes. The same duration is used for all deep stops. The first deep stop is placed at half the distance between the maximum depth and the ceiling depth, provided that the difference is at least 9m. On a no-stop dive it assumes a theoretical deco ceiling of 3m. Once the deep stop is completed, the next deep stop will again be introduced half-way to the ceiling, and so on, using the deepest depth since the last deep stop as the reference. The algorithm continuously updates the deep-stop calculation. Therefore, when there is a descent after a deep stop, the next deep stop will also be adjusted downwards. Once the ceiling depth is reached, continuous decompression is employed for staging the end of the profile. The minimum depth to make a deep stop is 21m. It is worth mentioning that these deep stops are additional safety stops and, if carried out or missed, do not affect Suunto's RGBM (Reduced Gradient Bubble Model) underlying decompression algorithm.

Aside from the new software and change of colour, all the other functions of the Vytec DS are the same as the conventional Vytec. The D6, on the other hand, has been brought in as a smaller brother to the D9. It employs the same deep-stop algorithms but loses the wireless (gas integrated) functionality, third gas switch option, titanium case (replaced with stainless steel) and is rated to 150m (the D9 is to 200m). The benefits it brings, however, are that it is considerably slimmer and the price drops by a whopping £280 without the Dive Manager PC interface, or by a generous £213 with it.

We tested both the Vytec DS and pre-production version of the D6 alongside my D9. Not surprisingly, they all gave very similar readings. Interestingly, though, the Vytec DS was a bit more pessimistic on my remaining air supply but that could be down to the tolerance in the transmitters as it also gave a slightly lower pressure reading. Suunto fans will be delighted with these two new computers. If you prefer a larger display the Vytec DS allows adventurous diving with all the functionality one would require while the D6 brings affordability with only marginal loss of features compared with the D9.

Verdict

DS £399, with transmitter £699
Large display and packed with functions
Value: 8/10
Performance: 10/10

D6 £470
Good value, with lots of features
Value: 9/10
Performance: 9/10

Contact: Suunto 01420 587272
Website: www.suunto.com