Almost every recreational diver is familiar with dive computers. Diver-carried computers have become a way of life. The question is: do dive computers have a role in technical diving?
First of all, let me define the scope of this discussion so we’re all on the same page. Let’s limit our discussion to diver-carried computers designed for technical diving. These computers are capable of tracking multiple gasses and computing a decompression schedule. Within this group of dive computers, we can further divide them into computers that are capable of calculating deco schedules for helium-based mixes (“trimix” computers) and those that only deal with mixes containing oxygen and nitrogen (“nitrox” computers). The Liquivision X1, Dive Rite Nitek X and Delta P’s VR3 are examples of so-called “trimix computers” while Dive Rite’s Nitek Duo and Trio are examples of multigas “nitrox” computers.
Next, let me dismiss the idea of using recreational dive computers (i.e. single gas, no decompression) in a technical diving setting (i.e. multiple gasses including trimix and staged decompression). Trying to do this is like using a hammer to drive in a screw: it’s simply the wrong tool for the job.
I am also not going to discuss specific brands and models, nor am I going to attempt to provide some sort of “Buyer’s Guide.” I’m going to discuss the general debate centering on technical dive computers vs. tables and bottom timers.
Technical dives are complex and require lots of planning. You have to choose your bottom gas, deco gas(ses), calculate a decompression schedule, calculate the volume of each gas required and factor in contingency plans. Historically, divers have used computer programs on a desktop computer to run various scenarios and come up with the most viable plan for a given set of dive parameters. The software generates a deco schedule which is transferred to a slate or waterproof notebook. During the dive, the diver uses a simple timer and depth gauge to follow the plan.
Since the advent of dive computers specifically designed for technical diving, the debate has raged between the “computer” crowd and the “bottom timer and tables” camp. The computer devotees cite the main advantages of wearing a computer as flexibility (i.e. endless contingency plans on my wrist), accuracy (the computer is calculating deco based on actual depth/time rather than pre-cut tables of what I think depth/time will be) and elimination of human error. The bottom timer advocates cite economy (“I can buy a lot of bottom timers for the cost of one computer”), lack of necessity (tables work fine, why change?) and the notion that a dive computer will become a crutch for divers. Both sides make valid points. Let’s look at a few of these points.
Flexibility Computers do offer great flexibility. If your depth or bottom time should deviate from the planned time or depth, the computer will modify the deco schedule to reflect such variances. If a planned deco gas is not available for some reason, the computer will again modify the deco schedule to account for the loss of this gas. BUT, argue the computer opponents, if you really understand deco theory, you should be able to calculate those kinds of table “tweaks” yourself underwater using only the dive computer between you ears. This leads into the next argument against using computers.
Computers are nothing more than crutches for inept divers. Some argue that if you understand decompression theory and how to apply it, you can generate a reasonable deco schedule off the top of your head, or, as in the example above, modify an existing schedule to account for changes in the dive plan. I think this premise takes a sound concept and takes it to absurd proportions. I do agree that all technical divers should thoroughly understand decompression theory and its application. I believe it is imperative to have a solid foundation in deco theory before one can intelligently use a dive computer. I can’t imagine any instructor advocating that students buy computers in order to avoid learning decompression theory. Remember, a dive computer is a tool. Tools are stupid; they rely on the craftsman to have the skill to use them properly.
Accuracy Proponents of dive computers point out that computers provide a more accurate depiction of the actual dive. Most technical divers using desktop software plan a dive as a square profile, that is, the diver descends to maximum depth, remains there for the entire bottom time, and then begins a direct ascent to the surface. In reality, the depths of the dive may vary during the dive and the square profile may generate an unnecessarily long deco schedule. The computer, however, is constantly calculating and re-calculating the deco schedule based on current dive parameters.
No discussion of dive computers would be complete without mentioning cost. There’s no denying the fact that computers for technical diving are expensive. While a multi-gas nitrox computer may only cost several hundred dollars, a sophisticated multi-gas trimix computer will set you back over one thousand dollars, with some close to two thousand. Are dive computers worth the expense? That’s a personal decision each diver must make for him/herself.
Whichever tool you decide to use to manage decompression planning, it must be a team decision. Team members must communicate and agree on procedures for the dive. All members of the dive team must use the same gasses, follow the same profile and use the same decompression planning tools.
No matter what dive computer or desktop software package you use, you should:
• Understand decompression theory and its application
• Know how the software you are using functions and use it only within its stated parameters
• Consult with dive team members when planning dives so you are all on the same page
• Use decompression planning tools conservatively
• Dive within the capabilities, limitations and certification levels of the least experienced team member
In technical diving, there should be no egos within the team. You should be absolutely comfortable talking with and asking questions of your teammates. After all, you are placing your life in their hands and they are doing likewise.