IN THE 1990S, Audi developed a new small car model. It took a bold step in deciding to bolt the bonnet shut. It concluded that todays car engines were too complicated for the owner to fiddle about with, and that there was little the driver could or should do.
So the A2 model was built with an openable front grille, so that the driver could check engine oil and brake and cooler fluid, and refill the screenwash. Thats it. The A2 was for those who wished to focus on driving - and nothing else.
Jonas Brandt and his crew in Poseidons R&D department followed similar principles when they developed their new rebreather. Discovery VI is a fully closed, fully automatic rebreather for sports divers who want to go to a maximum of 40m without decompression. The number of procedures to be performed by the diver has been minimised - to decrease the risk of human error.
Poseidon believes that the typical Discovery diver will be a middle-aged gentleman who has been diving for some time and wants to spice up
his diving, but is not interested in submersing himself into technical diving, great depths and prolonged decompressions.
Poseidon also wanted to design a breathing machine that could be handled by someone who had never even tried diving before. As long as the Discovery functions normally, the user should feel no need to pay more attention to it than he would to the pressure gauge with open-circuit scuba gear. An experienced diver should need to spend no more than 15 minutes assembling his Discovery, and preparing it for the dive.

A closed-circuit rebreather is an advanced and complicated piece of equipment. Up to now the intended customer base has been relaxed about fiddling with settings, preparations and pre-dive tests. So how do you design a rebreather for those who are less relaxed
According to Poseidon, the solution is called Pre Dive. The Discovery VI needs slightly more than two minutes to pass a self-test of approximately 30 items before you are allowed to start the dive. The test includes leak checks, oxygen sensors, gas pressure, battery condition, software and so on. Unless everything is OK, the message will be Stop.
We encountered this ourselves before we could splash into the Poseidon pool on our try-out dive. The Discovery needed three test runs before it was entirely satisfied with the set-up. Among other things, one of the O-rings in the gas loop turned out to have a tiny leak.
To minimise the risk of errors in refilling and packing of the scrubber, Discovery is supplied with ready-to-use scrubber canisters that last for three to six hours. The price of a scrubber canister is about £21. Add to this the cost of refilling the gas supply, and you have a running cost of around £8 per hour.
We were pleasantly surprised when some interesting and unexpected customer groups started making requests. We didnt have those in mind when we developed the Discovery - military units and rescue services. They have shown a keen interest in our plug and play concept, says Jens Sjöblom, Poseidons Sales Manager.
The Discovery has a unique design, in that it has only two oxygen sensors, but these are subject to constant recalibration while it is in use.
This is done using micro-valves that blow minute amounts of pure oxygen and air alternately across the face of the cells, so giving two calibration points. It was a system originally conceived by cave-diving veteran Bill Stone, the inventor and designer of the original and very complex CIS-Lunar rebreather.
Initially it had been intended that the Discovery would have a single sensor, so reliable was this concept thought to be. Market research since proved to Poseidon that the diving public had yet to be convinced that a solitary cell would be
up to the job, and a second cell was therefore added to the design.

Finally it was time for the test dive. I spent a few minutes at the surface, breathing from the system in open-circuit mode. Then I turned the knob on the mouthpiece to closed-circuit. I emptied my BC in the usual way and descended slowly.
At this point, any similarity with procedures from my previous 17 years of diving ended. I had always used my BC to make rough buoyancy adjustments, and the volume of my lungs to make the fine buoyancy adjustments. That doesnt work with a rebreather. The volume of my lungs plus the volume of the counterlung (breathing bag) remains constant during every breath.
I experienced some very instructive minutes in beginners mode before I found my correct balance and buoyancy. Then I could focus on what it was like to dive closed-circuit.
The first thing to strike me was the silence. It was deafening! I was used to a steady stream of bubbles rushing past my mask and ears, and my first reaction was a feeling that something was wrong.
My next impression of the Discovery was its lightness. I could feel no difference in weight or bulkiness between the unit and an open-circuit system, and it fitted well, practically inviting me to perform acrobatic exercises. Hovering a couple of inches above the pool floor was easy.
Before kitting up, I had been sure that the mouthpiece would feel heavy. It is quite a bulky piece of gear to hold clenched between the teeth, but during our brief test dive I felt no symptoms of jaw fatigue.

On the Discovery, most of the complicated decisions are managed by the dive computer. Nevertheless, there are many routines with which divers have to be well acquainted before they can use a rebreather correctly.
This is why you have to pass a special course before you are allowed to use the Discovery on your own.
For those without previous diving experience, the course lasts for 4-5 days, while for experienced divers, its a bit less. Poseidon is producing educational materials for TDI and IANTD and others, and has around 40 instructor-trainers and more than 50 instructors lined up to take on students. Discovery will be in full production very soon, and I dont expect this to be a bottleneck for our expansion, says Jens Sjöblom.
To keep your Discovery active, you have to submit it for inspection and service of the first and second stages every two years.
The dive computer keeps tabs on the interval, and if you neglect or forget the service, the Discovery will refuse to dive with you.

The work on the new rebreather started in 2006, since when some 60 more or less functional prototypes have been tested. Initially, Poseidon built a rebreather for pure oxygen without electronics, just to carry out mechanical tests and check comfort. It also spent some time developing the mouthpiece.
That was one item we identified as difficult very early on, says Jonas Brandt, Technical Manager and head of the Discovery project We intended to design something that no one had made before.
The company wanted a mouthpiece that would perform well in closed-circuit mode but would also meet the requirements of EN-250 in open-circuit mode. The resulting unit boasts better breathing-resistance performance than a separate Xstream unit, according to Poseidon.
The company has spent around £2.3 million on developing the Discovery. Only one part of the rebreather is standard-issue off the shelf - the first stage. The rest has been developed along the way, with parts including the electronics produced around Sweden, and final assembly is done at the Poseidon factory in Gothenburg.
The first drafts for the design and performance of the new rebreather were outlined long ago. Cost specifications and a projected price level for the final product had already been calculated at that stage, and Brandt concedes that the original calculated cost was exceeded by 5-10%.
With production not yet running at full speed, today the customer has to pay around £4700.
Poseidon professes to be unconcerned that the price tag could deter buyers. With gas bottles, regulators and a fully fledged dive computer included in the price, and the possibility of doing extended dives of up to three hours, it feels that the customer is getting a good deal.
Discovery VI will be available from Poseidon Premium Dealers only. The company estimates that there are 15 million divers worldwide, of whom 10 million are active. If just 1% of these could be persuaded to dive closed-circuit, the manufacturer would be kept busy for a long time to come.
With present capacity, Poseidon can churn out 2000 units a year, but as this is a new and complicated product, it has decided to start with an initial production run of 400.

One of the more controversial design solutions was to provide the rebreather with two oxygen sensors, rather than the three that have almost become standard among other manufacturers.
We decided very early during the design process to reduce the number of oxygen sensors, says Jonas Brandt. We actually discussed using a single sensor only, but we didnt think the market was ready to accept that, so we finally agreed on two.
This is how we reasoned: just because you have three sensors, there is no reason to believe that two are always good and one is bad. It may very well be two bad ones, and only one is good.

In the autumn of 2007, Poseidon announced that the rebreather was ready to be introduced. So what happened
For six months, we focused entirely on figuring out how the sensors behave, says Brandt. Consequently, today we know things about the sensors of which even their manufacturers are totally unaware. We have tested them in hot saunas as well as in deep-freezes, only to collect data on how they react under various conditions.
A lot of this project is about calibration and validation. We dont want to end up in a situation where 300 customers all over the world are unable to use their rebreathers, just because sensor readings are pointing in different directions.
The launch was delayed for a year, which allowed Poseidon to test and fine-tune its new product further. And the market has matured. Poseidon monitored the arguments on international dive forums, on which many of the more conservative posters discarded the whole project as a fiasco.
The Discovery may be a rebreather with a lot of unorthodox and innovative solutions, but general opinion today seems to have turned around.
We carried out meticulous research when we started working on the rebreather, Jens Sjöblom tells us. We wanted to establish the facts behind many of the truths that were flourishing.
Certainly, sport divers are a traditionalist bunch. In many aspects, the rebreather community is even more so. Further, lots of rumours abound. Some are plainly wrong, and a few are utterly dangerous.
Poseidon is the only manufacturer offering a closed-circuit rebreather specially developed for recreational diving, but it says it doesnt mind if others join in and develop their own models.
The more brands trying to reach the market, the more attention will be generated around CCR, and this, it believes, will be to everybodys benefit.

Many divers with a new Discovery VI would surely love to take it on their next diving holiday. It comes in a hard-shell transport case with foam plastic inside, intended to fully protect it at airports.
However, one fact makes extensive air travel problematic - the units 18kg weight, on top of the rest of your dive gear and personal items.
You can remove the two cylinders and
scrubber canister, reducing the weight to a measly 8kg, and Poseidon reckons many customers will take this route. For this reason, it has put a lot of effort into signing up dive centres and liveaboards around the world to provide gas tanks, scrubber containers and spare parts.
The paint is still wet on the first Discovery VI units, but plans are already advanced to develop a trimix model for diving to 60m. Poseidon says that it needs only to adjust the computer software.
Nothing has yet been decided about when the trimix version will be released. For those who dont think 60m is deep enough, a third-party enterprise is working on hardware and software for depths of 100 and perhaps even 300m.

As DIVER went to press, we heard reports that the Discovery VI had just won its CE mark! Poseidon Diving Systems,