Dive Computers - Pros and Cons

[Deep Blue]

Chris,

You make some good points on the power of deco on deeper recreational depth wrecks. When I teach my decompression procedures, I do not frame it as a deep class. I personally have a strong belief that if you are going to dive deeper than 150 feet (I prefer if deeper than 130 feet) that you use helium in your breathing mix.

The most powerful aspect of the deco class that I teach is the ability to plan dives in the 130 foot range with respectable bottom times and still get out of the water in less than an hour. Even if you are on a recreational boat, as long as you are first in, limit your dive time to under an hour, you shouldn't get too many evil stares as you get out.

A great example is planning a dive on the Wisconsin for 130 feet, you can do a 30 minute bottom time, with EAN28 and carry 1 40 cubic foot bottle of EAN50 and your total deco is 12 minutes. You are out of the water in 45 minutes. This dive could be done on one big single, the Pressed Steel E150 comes to mind with room to spare the Totally cool even on the most recreational boat.

If you did that dive with air, and no deco gas, as would a person relying totally on their computer, you have 36 minutes of deco and at total dive time of 67 minutes for the same bottom dive!!!! For this dive you would need to carry 180 cubic feet of back gas to cover the dive and a reserve.

Gaining an understanding of gas planning and the effect of gas selection as well as dive planning suffers greatly when a diver relies too heavily on the computer on their wrist, and forgets about the one between their ears!!!!