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DIVE COMPUTERS VS. DIVE TABLES

By: Sean Harrison SDI/TDI

By: Sean Harrison SDI/TDI

Picture this – I’m riding to the dive site on my horse and buggy, and calculating my no decompression limits on my abacus. If you think that takes time, that’s nothing, it’s chiseling my dive plan into my stone tablet – now that’s a real hassle. But hey, on the bright side, I don’t need a weight belt when I carry my dive plan!

This is all in fun but gets to the point that human nature is to advance, to learn and to progress, and with this comes change. Perhaps the most significant change in our industry was the introduction of the dive computer. Why was it so important? Because before we had it – we, as recreational divers, used dive tables which had some significant limiting factors. Here are just a couple of examples: they were developed for “square profiles” (where the diver hits the deepest depth and stays there for the total time allotted) and, the information the tables were built upon was derived from young male divers. Dive tables are by no means obsolete; they still have their place in diving. For instance, they are critical in planning a technical dive where the diver’s entire time may be spent at maximum depth, and they are needed to explain the evolution of diving and their role in history.

Dive tables are just one example of an advancement that has improved safety and made diving more accessible to a wider range of people. Some other notable advances are K valves, jacket and backmount BC’s, and the octopus. Some other items gaining popularity include personal emergency position indicating radio beacon (EPIRB), diver VHF radios, and surface marker buoys (SMB).

Personal dive computers not only improved the safety of diving by tracking in real time what the diver was doing, they also made it easier for the diver to log their dives, first by providing a dive log and then by allowing dives to be downloaded to a computer. Further advancements with some computers allowed for multiple gases to be used, switches from one gas to another, wireless (and wired) air pressure, air consumption rates and even heart rate monitoring. So these are the bells and whistles, but what about reliability?

Along with the advancement of features, dive computers evolved in their reliability as well. The early computers had mechanical on/off switches and several areas where water could infiltrate the computer causing a flood and a rapid failure. There have also been developments in battery technology. These amount to better overall reliability and fewer failures. Nothing is “bullet proof” so you will continue to hear people claim that computers fail, but so will your GPS, your car, and your phone. What needs to be considered is how often they fail, and with dive computers, it is not often.

The question you want to ask yourself is, do you want to learn with the most modern equipment that comes with the additional safety, features and benefits built in or… do you want to learn the old way which you will have to practice more often or get retrained on every time you want to dive? Why do I say retrain? If you learned using the tables, try this exercise. You do your first dive to 16 metres/54 feet for 25 minutes; you saw something during that dive you really want to see again so you plan your next dive to 15 metres/49 feet for 30 minutes, what’s your surface interval?

Go out, enjoy your dives, have fun and do it often, and leave the complicated planning part to the dive computer manufacturers and the technical divers (they love writing everything out on slates).

-Sean Harrison SDI/TDI