If he had the tables with him and knew how to use them he would have had a plan B. If he was never taught how to use them then that option did not exist for him.
What tables would an OW diver have that would have helped him do his second dive? According to the PADI RDP (I believe), he went into deco on his first dive.
Even if the OP were diving with two computers in this case it probably would not have helped. If he made every dive with identical computers dialed into the same setting what are the odds that he would have changed both batteries at the same time? I think those odds would have been about 100%.
Diving with two computers is the vastly better answer than telling him to learn how to use tables. In this specific scenario, the tables say he was in deco, so he was done for the day. If he'd had a second computer, that was setup correctly (meaning, as he intended it to be), presumably (because he said he did it before), he could have just done the second dive with his primary DC in gauge mode, and using his secondary DC for NDL info. IOW, tables? No second dive. Backup DC? Yes on a second dive.
It seems like a more common scenario would be that his primary computer actually died for some reason (versus being setup wrong). In that scenario, tables are, again, useless because he would be back on the surface after his first dive with no record of his BT or max depth. So, no way to use tables to work out a second dive. Unless you would suggest using the dive log from his buddy's DC... So, again we're back to tables wouldn't help but diving with two computers would.
Lastly, I dive with 2 computers. And I would say that the chances of me diving with both of them having brand new batteries at the same time is about 1%. And that 1 percent is allowing for, either, diving in the pool to make sure they are both good, or a total fluke that both DCs happened to literally die at the same time. My DCs are not identical. Other than some tech divers with 2 Shearwaters (or similar), who dives with two identical computers?? Even if they were identical, I think it highly unlikely that both batteries would go at the same time. However, even if they both showed Low Battery at the same time, I would still change one first, then the other. Diving with 2 computers that have both just been serviced seems like not the best idea at all. There's always a chance the service could result in a problem, so it will always be better to dive one freshly serviced and one "known good".
So, again, it seems to me that, if you're going to use a DC at all, then there is really no NEED (for an OW Rec diver) to learn or use tables. For anyone who is concerned about missing out on some diving because their DC died, the best solution is to dive two DCs. The only way to even be close to as good, using tables, is if you use a DC and you also dive with a depth gauge that records max depth and a bottom timer. And that will still not give you nearly as much BT, on your second dive, as if you spent just a little more money and got a cheap DC as a backup, instead of the depth gauge and BT. Unless your first dive was totally a square profile. Then using tables might be somewhere close to as good. Maybe.
---------- Post added April 12th, 2015 at 01:04 PM ----------
3.) He never received instruction in the first place about what the computer was telling him.
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I see this whole episode as an instructional problem, or rather, a lack of instructional problem. I did not intend to point my finger at any particular instructor.
So, if you had been his instructor, back 1000+ dives ago, he wouldn't have done what he did? Color me skeptical. People do stuff all the time that they were thoroughly and well instructed not to do. ESPECIALLY, when they've been engaging in whatever activity we're talking about for long enough to feel confident in their own skills.
