Sharing a Dive Computer

[GrumpyOldGuy]

No.

One of the primary safety directives is you are to be responsible for your own safety. You cannot do this sharing a dive computer.

 

[Mr Carcharodon]

Or you could just stay shallow enough that decompression is not an issue. Of course then you are not using it as a computer really.

 

[oddible]

Curious answers though uniform. In fact, the PADI book says you don't need a dive computer at all - so the imperative that I'm hearing in this thread that one MUST dive with a dive computer is a bit odd. I could certainly use dive tables and RDP and identify my maximum depth before I go and ensure that we never cross that line and come up well before the NDL. The computer is a convenience that has become a standard (which is why we bought one at all) that allows people to stay down longer because of higher precision while achieving additional safetly due to warnings and alerts (the warnings and alerts may be the most important feature here particularly in ascent).

So basically what I'm hearing in this thread is NEVER, EVER dive without a computer?

 

[BabyDuck]

no, that's not what's being said. it is fine for one of you to use the computer and the other to use tables.

it is *not* fine to both use the same computer.

 

[ptyx]

So basically what I'm hearing in this thread is NEVER, EVER dive without a computer?

You are hearing that diving with your instruments attached to someone else wrist isn't a good idea.

One diver with a computer, the other with watch+depth gauge+RDP is ok. But that's not what you mean by 2 divers on one computer.

*If* you're 100% certain you can maintain depth discipline (computer always the deepest, controlled ascents) and team cohesion (never ever loose your buddy), then from a pure decompression perspective it is safe. After all, that's what happens on a 'discover scuba' dive.

But can you? It is harder than it sounds, especially if both of you are freshly certified. And what do you do if you break those rules?

 

[Doubler]

I went back and re-read every post, didn't see where it said you must dive with a computer. I read if you dive with a computer don't share. If you both WANT, not NEED, a computer rent one, don't share. You are correct, you do not need a computer to dive. You may use tables if you wish but you will have a square profile and unfortunately dives are usually not square. A very simple way to look at it is a computer is an optional (not in my world) safety device which helps you safely increase bottom time, monitor depth change rates, and determine SIT time based on off gasing tissue algorithms. While a computer may be optional to the diver, as the PADI book states, it is a requirement at several resorts and dive boats.

 

[oddible]

Thanks all, I've been reading these boards a lot to take advantage of the experience of so many dives present here and I haven't even left the pool yet. I'm not being difficult, I appreciate the clarification. One consistent theme I read in nearly every post throughout this board is, don't mess around, leave as few variables as possible. Which is why we bought the dive computer in the first place. I suspect that renting an extra one is good on a variety of levels - to try out some new brands as well as to provide an extra measure of safety without having to deal with, as you say, a square profile. I appreciate the advice.

 

[Bonairetrip]

No. Rent until you can afford to buy. How ever, you can share it in the lines of she gets to use the reg setup with the computer one dive, and the next dive you take the setup. That way you can both get used to using the computer and see if you like the computer or not. Why buy the same one twice if one of you dont like it.

Not entirely true. You must be very cautious in trading off dive to dive. In order for this to work, practically speaking, both computers will need to read that you are fully off gassed before you switch. Failing to do that runs the real risk that your computer will understate any deco obligation.

 

[lmorin]

I think the overlooked question here is whether or not you have a fall-back position if the one computer fails. Secondarily, do you know how to actually use the computer you have purchased? IMHO, sure, you can use a single computer for two people if you stay reasonably close together and don't push the dive limits. It also should be remembered that the computer is simply a tool which, used properly, can make certain aspects of dive safety easier. If you know how to use tables, and they plus a timer are the fallback position, then you don't need even one computer.

 

[DiveMaven]

I could certainly use dive tables and RDP and identify my maximum depth before I go and ensure that we never cross that line and come up well before the NDL.

If you do this, then one of you is diving with a computer and one is diving using the tables. Since both divers would then follow the table profiles (square) then neither of you is using the computer for anything except as a depth gauge and ascent alarm. You're both basically following the limits set by the tables since its the most conservative model, regardless of whether the dive is "square" or not.

The computer is a convenience that has become a standard (which is why we bought one at all) that allows people to stay down longer because of higher precision while achieving additional safetly due to warnings and alerts (the warnings and alerts may be the most important feature here particularly in ascent).

Yes, the point of having a computer is that it calculates NDL for multi-level profiles giving the diver more bottom time. However, this is ONLY for the diver wearing the computer, which means if they are buddied with someone diving the tables, both divers follow the tables and come up when the tables say to, NOT the computer.

So you can't have it both ways. You dive your OWN profile, not someone else's. You plan your dive based on the gear your buddy team has, following the most conservative model.

As another example: I dive with an Oceanic computer. If I have a buddy with a Suunto, we'll be following his computer's algorithm, not mine since his is much more conservative. If his computer locks him out of diving due to pushing the limits and mine doesn't, we're done diving. We plan our dives and follow the more conservative limits, regardless of what my computer says.