Dive Computers Make Diving Safer

Like cellphones, dive computers have evolved from brick-sized devices to something not much bigger than a sports watch. And even though they're smaller, they pack more computing power than ever before. If you're a recently minted diver, you probably already own basic equipment, but just as I did when I certified, you likely have held off on dropping the big bucks required for a dive a computer. I recommend that you start saving!

Although every model differs, all dive computers provide a wealth of information which assist divers in making safe decisions. Their primary purpose is to calculate surface intervals and depth/time trade-offs for repetitive dives. As you know from your training, these calculations can be done with a card or wheel, but there's nothing simpler than a dive computer that turns itself on automatically and then measures your dive depths and times. Even better, you can sit topside on the boat eating and rehydrating while your dive computer does all the work to figure out when you can dive again.

Benefits of a Dive Computer

Aside from the cool factor, convenience and safety are important motivators for the purchase of a dive computer. In case you're wondering why you should bother, here are some features:

• Depth: The key here is that the dive depths are recorded regularly and each data point is use in calculations rather than just your max depth.
• Dive Time: Time flies underwater, but your computer will automatically start and stop.
• Surface Time: Let your computer figure out when you can do the next dive.
• Nitrox: Adjust the calculations based on your nitrogen and oxygen mix.
• Alarms: Beeps, flashing, or vibrations can alert you to some predefined condition such as max depth, time remaining, dive time, and safety stop depth. Other alarms are automatic and can't be turned off such as ascending too fast or exceeding decompression limits.
• Recording Dive Profiles: If you're the type that keeps track of everything in your log, your dive computer will come in handy as it can record multiple dives for later download to your computer.
• Navigation: Some computers include a compass. One less thing to carry on your console.

Dive Computers Aren't Perfect

It's certainly true that a dive computer eliminates the mistakes that occur when people use cards or wheels to figure things out. But they introduce a different set of problems:

• No automatic safety margin. By definition, dive computers are precise so gone are the dive time and depth buffers that manual calculations can include.
• Different computers use different algorithms. Not that the names mean anything to the average diver (me included), but for reference common algorithms include: Buhlmann, Reduced Gradient Bubble Model (RGBM), Vary Permeability Model (VPM), and modified Haldanean/DSAT. In addition, some companies modify these common ones to meet their own specifications. As you can imagine, different models result in different levels of “aggressiveness” in how long and how deep you can dive. What's more, none of them are based on your body's actual capabilities, that is, they all use theoretical models based on averages.
• A dive computer is only useful if the wearer understands its use. For example, if you forget to adjust the altitude, your dive computer isn't going to be all that useful.

Overall, I think you'll want to get a dive computer if you plan to dive regularly. In the near future I hope to look at different models and provide commentary on them. However, no matter what you buy, be sure to treat it like a critical safety device and not like you DVD player with the blinking clock that was never set.