In 1995, when my first article with this title was published, I cited the two major reasons behind my argument were that dive computers encourage divers to skip some vital aspects of dive planning; and, in any event, dive computers twist the decompression algorithm so badly that they were conservative to the point of being potentially dangerous.

That first article didn’t cause much of a stir, just a few emails and phone calls from divers who thought my ideas were crazy and a marketing letter from an equipment manufacturer offering me their latest dive computer as a demo!

It’s true that the functions and features of dive computers have progressed considerably since the mid-90s. It really seems from today’s vantage point that we were back in the stone ages then. Now there are models that manage multiple gases for decompression, figure helium bottom mixes into the calculations, and some that use bubble model algorithms like VPM.

However, with eight years more experience teaching and diving, the arguments against using computers for technical diving remain the same and are as strong as ever.

Let’s recap the major challenges: Divers seem to use computers primarily because they don’t have to plan their decompression schedule: the computer does it for them. This may sound wonderful. But think about what this means in a dive involving multiple stops and multiple gas switches… The diver has little or no way to play with “what if” type scenarios nor can she easily look at the impact of something like a late or early gas switch, using a second or third decompression gas or dropping the PO2 in her bottom mix to better manage CNS stress.

In fact, when you look at it from that perspective, by using a computer, she has just handed over responsibility for DCS planning and CNS risk management to her computer. She will gain zero experience in both these areas by using a computer. This dependence on a “quick fix solution” – especially in the case of less experienced technical divers – discourages the necessary fundamental understanding of decompression theory and gas management.

I think the “training and understanding” issues are pretty compelling, but there is one even more grave shortcoming that we need to get out in the open. But before we move on to that, there are a couple of other small points. Dive computers are expensive. I see people with two or three of them! That’s a trip to Truk Lagoon right there. Computer manufacturers also seem to have lost touch with their customer base and what they want and need from computers. Seems to me the screens are getting smaller, but there’s more and more information crammed into the available real estate. And most of the information on-screen is totally irrelevant – for instance, do you really need blinking notification that your CNS level is at 3% in lieu of notification that your depth right now is 210 feet?

OK. Now we will look at the big issue.

Computers twist the algorithm to a point that it will create a padded decompression obligation. Often that padding will be an obscene distortion of the algorithm. With an uneducated diver who got into staged decompression by accident, this might be a bonus, but for someone trained in decompression theory and someone who understands the vagaries of decompression planning, spitting out a decompression schedule with training wheels attached is ridiculous. And is potentially dangerous.

I have my own theory as to why this is and it really has to do with risk management. Unfortunately, rather than managing the diver’s exposure to risks like DCS and CNS toxicity, it’s about limiting the computer company’s risk in court!

Most dive computers – all the ones I’ve seen -- come with warnings that we should not use them for decompression diving. This is a little strange since quite often the instructions that are packaged with computers talk about how those computers handle decompression diving. Anyway, what those instructions do not explain is that the manufacturer’s legal department have twisted things so that if you should sue them, they can point out to a jury that: “Our computers are designed to keep divers in the water 50% longer than the standard algorithm recommends.” Since the jury will not be divers, it only remains for the company’s lawyers to roll out “an expert” to explain to them that if 10 minutes of deco is called for, then 15 minutes MUST be better! There is no consideration given for thermal stress, gas management, CNS toxicity.

In short, this simplistic view of the world of technical diving doesn’t work too well where I do most of my diving and teaching – which is in North America’s huge inland fresh water seas, and among the best wreck diving in the world.

To be fair, computers do have a place in my world… usually at the end of a line in about 20 feet of water clearing while the rest of the team, sits drinking Gatorade and watching video from the dive

My advice, get a digital bottom timer, buy a copy of V-planner for your PC and learn the face of the algorithm so you can plan your dives properly.

Take care, and Dive Smart.