Suunto Mosquito

When the first dive computers started to appear back in the mid-Eighties they were cumbersome and greeted with great scepticism. However, they were quickly adopted for multilevel diving as they gave considerably more total dive time.

At the time Finnish manufacturer Suunto introduced its SME model, which was by far the smallest unit available – giving all the required information in a compact display. Now, more than ten years on, Suunto is one of the largest manufacturers of dive computers in the world and has recently launched the Mosquito, an incredibly powerful computer the size of a wristwatch – incidentally, it also tells the time!

The Mosquito’s body is made from carbon fibre as opposed to the stainless-steel body of its more expensive sibling, the Stinger, and it is as compact as the average sports watch. One major advantage it has over most of its rivals is its user-changeable battery. A replacement battery kit (including cover and O-ring) costs £6 and Suunto recommends that the battery is replaced every year or when the battery indicator displays ‘low’, whichever is the sooner.

What does it do?
For a free-diver it’s a stopwatch, basic depth gauge and timer. For the diver it has a full decompression capacity for both air and nitrox diving, and by using additional software it can be connected to a PC to record all aspects of dives undertaken. The computer can also be personalized, for instance giving an audible alarm at a selected maximum depth. It also provides water temperature, no-fly time, dive planning, fast-ascent warning, dual time zones and wake-up alarm. The display has what is called an ‘electroluminescent’ illumination button (back light to you and me) for night or low-visibility diving. Waterproof to 100m, it caters for all but the most adventurous of divers. Unlike the Stinger, it does not offer a gauge mode for trimix divers, and the logbook profile sampling rate is not adjustable.

How did it perform?
To test the Mosquito I completed 32 dives at various depths to a maximum of 51m over a 12-day period, comparing it on the dives to the older Suunto SME and Solution computers. The first thing I noticed was, despite its smaller display, it is easy to read.

On the first dive its performance was almost identical to that of the older models, with the exception of an advisory three-minute safety stop. If this is ignored the computer will function as normal. However, as the diving progressed, the Mosquito gave considerably longer stops. According to Suunto the newer, advanced algorithms used in this computer take into consideration a multitude of complex dive profiles including rates of ascent.

One extremely useful feature, which is unique to Suunto, is that the computer tells the diver whether the decompression stop time is increasing or decreasing once a stop is necessary. If, for example, during a dive to 30m the display reads that a stop has to be carried out at, say, 3m for 5 minutes, the ascent time reading flashes. On ascending the diver may find that at 11m the ascent time reading stops flashing – this means that the stop time is no longer increasing as you are above the so-called decompression floor. Obviously if you spend a long time at this new depth the ascent time display may start to flash again, meaning that the total stop time is increasing. If you now ascend until the ascent time icon ceases to flash, the stop time advised will remain the same.

How does it work?
All dive computers are based on an algorithm or model which simulates the rate at which your body washes nitrogen out of your system. Suunto bases the Mosquito on the Haldanian system, one of the most widely accepted algorithms, but has added further safety measures based on the latest research, particularly into the body’s ability to generate micro-bubbles on nitrogen.

To limit the possibility of a diver producing these potentially dangerous, tiny bubbles of nitrogen but still allowing a reasonable time under water, Suunto has introduced a control system devised by Dr Bruce Weinke of Los Alamos National Laboratory, New Mexico in the US. It calls this the Suunto Reduced Gradient Bubble Model (SRGBM) and it monitors the diver’s behaviour during a dive. If the ascent rate is violated it insists on a safety stop to help reduce micro-bubble production before surfacing.

There are also four more protection systems which come into play when you are at the surface. The first is the ‘slow out-gassing model’ which takes into account that the process of getting rid of nitrogen dissolved in the bloodstream is slowed by micro-bubbles which are washed to the lungs. The lungs act as a very efficient filter catching micro-bubbles to prevent them getting into the arterial circulation – very dangerous! The other three systems are concerned with repetitive diving, reverse profiles and multi-day diving. Particularly nifty is the multi-day system. This acts to control micro-nuclei, which are thought to be pre-existing gas seeds, that exist in all people (divers and non-divers alike).

Diving (or compression and decompression) is thought to raise the energy level of the micro-nuclei and excite them into life to become micro-bubbles. Their next stage of growth would be to become out-of-control decompression illness bubbles. Nasty! This is a long-term consideration, which the Mosquito takes into account for 100 hours after the last dive. In general, the practical implications for repetitive dives are that, depending on the diver’s previous behaviour, the time allowed in the water without a decompression stop can be reduced by between ten and 20
per cent (as much as four minutes on a 20-minute dive).

In spite of these advances Suunto acknowledges that our knowledge of decompression is far from complete, but insists that the Mosquito is a major step forward in diver safety. Clearly the Mosquito is going to give more conservative dive profiles than earlier computers. As the science of decompression advances, it makes good sense to make sure you are diving with a computer working on the latest information. We have all heard of people suffering decompression sickness when diving ‘within the limits of tables and computers’.

Suunto also takes into account that there are adverse personal factors which only the divers themselves can predict, such as workload, tiredness, dehydration, fitness, alcohol consumption, prescribed and over-the-counter drugs. So they have added a personal adjustment mode to make the decompression model even more conservative.

We reckon...

+ Compact and easily readable
User-changeable battery
New safer algorithms

– Not quite as stylish as the Stinger