Steve,
Quick tip...Instead of investing in a computer that you don`t really need...Try a simple bottom timer...
http://www.scubapro.com/americas/eng...al-depth-gauge
These devices show all the info you really need on a dive and can be purchased for less then $200...I often see them for sale used for little more then $100...
If you really think about it, depth, max depth, time is all you really need...these gauges give you all of the above and cheaper then a `puter....Its costs a lot of bucks to get into diving, so saving some here in there with smart purchases really helps...