Should I have a backup computer?

[drbill]

Years ago when I dove a single computer, the battery went out while I was on a long deco dive. This was totally unexpected since the remaining battery power indicated about 38%. I found out that the computer used an algorithm and didn't actually measure battery strength. The manual said you could still do a few dives when the battery indicator reached 0%! I found it was common for these computer batteries (not user replaceable) to die like that and informed the company of this.

Ever since then I have dived with computer redundancy for added safety. Sometimes I've used the same model, sometimes one more conservative than my primary.

 

[tursiops]

a recommendation is a suggestion, nothing more, nothing less. I maintain that "recommended" is in fact identical to "optional"

I think, if you will look carefully, that recommended is stronger than optional. Recommended implies it may very well help you. Optional is less strong.

You may find this interesting. History of the Safety Stop
The words on the PADI RDP are: "A safety stop... is required any time a diver comes within 3 pressure groups of a NDL and for any dive to a dpeth of 100 ft or greater." The words in the PADI OW Manual recommends a safety stop on virtually any dive, as a standard practice..