Buddy diving on their computer

[OldNSalty]

I noticed the OP has very few dives so he may have just been certified recently. I have heard that some agencies don't even teach tables any more, which I think is, well, silly to say the least.

Anyway, if by chance that is the case I just wanted to add that they are not difficult to learn and you really should do it (even if you decide to buy a computer later)

 

[mgmonk]

Well put

 

[Blackwood]

In my opinion the key point here is the word 'failure'.

You are training and planning for contingencies. To monitor ascent rates, stop times etc having one working one computer is better than having none. I can not see the value, reason or safe diving practice in planning a dive or series of dives with only one computer between a buddy team.

Hence your next part about practicing team skills.

well... we aren't just planning for contingencies. One person calls the deco profile (even for "non-deco" dives). However, we all know (based on our gauges) what the profile should be, and won't blindly follow the Deco Captain (unless our gauges fail).

But my main reason for posting is that I don't really feel that a few feet here or there makes a great deal of difference. Deco isn't black and white. It's a huge gray area.

 

[jepuskar]

Computers are great. Until they crap out. Smart divers check their tables before the dive, write down the info, and may well bring the tables with them in case the dive plan changes and can recalculate on the fly. Be a smart diver. Always.

That's smart if you have a mandatory decompression ceiling. If you're talking just rec diving, none of that is necessary.

 

[Coldwater_Canuck]

Not going to lie: I'd probably dive on someone elses computer if I was careful (by which I mean either ensure I am always on the same level or higher in the water or be very conservative with the times).

Tables are fine for boat dives, but I've found them absolutely useless for shore dives.

However, I now have a computer. After buying an expensive BCD and regulator, was low on money so got this guy: http://www.scubatoys.com/store/detail.asp?product_id=MaresM2. Not the sleekest looking computer and no air integration, but is full featured (including Nitrox) and should hold me over until I can afford a nice hoseless wrist unit (and function as a backup after that.

 

[sail-fish]

Hi Guys,

Thanks for all the replies.

Just to answer a few of the qestions, yes i'm a recreational diver, recently certified (18 or so dives) and not sure whats more interesting below the fiancee I just know i'm always there for some reason.

I did learn the tables but havnt used them yet as the first multi dives i've done were the last ones i did on reputable dive charter boat and hence the questions now.

I'm going to pull my tables out and re-learn them and also i like that trick with the slate. (used that to propose to my fiancee at the poor nights in nz - she is a marine bioligist who got me into diving )

Thanks for all the advice - really appreciate it.

Mike

 

[highlandfarmwv]

Tell her that you MUST be level or above her at all times, or you won't dive with her!!

 

[dumpsterDiver]

I'm amazed that some people (other than me) might think it is ok to use another person's computer. It all depends on how close to the no-deco limits you are diving. If she always has 15-20% additional no-deco time when she starts the ascent, and you know that you are very close to her profile then there should not be a problem.

However, if she is pushing the limits (which is not too hard on repetative dives), then I would think you need to follow the tables or be careful. You really need to understand your depth/time limits before the dive, to make an educated guess about how important a computer is.

I dive with my pre-teen boys and they have no computer, but they are with me and I am making sure we are not going to be pushing the limits, even if they should somehow follow a profile that is a little deepr than me.

 

[Coldwater_Canuck]

I'm amazed that some people (other than me) might think it is ok to use another person's computer. It all depends on how close to the no-deco limits you are diving. If she always has 15-20% additional no-deco time when she starts the ascent, and you know that you are very close to her profile then there should not be a problem.

However, if she is pushing the limits (which is not too hard on repetative dives), then I would think you need to follow the tables or be careful. You really need to understand your depth/time limits before the dive, to make an educated guess about how important a computer is.

I dive with my pre-teen boys and they have no computer, but they are with me and I am making sure we are not going to be pushing the limits, even if they should somehow follow a profile that is a little deepr than me.

That seems like a bit more of a reasonable response than just "NEVER DO IT!". Of course any agency or manufacturer's official response has to be "never do it" for liability reasons. But there's no magic with who's wearing it: the computers don't take individual divers into account, it is simply what depth they are at. If you are always level or above the person wearing the computer, there is really no difference to wearing it yourself: but can you trust yourself to stay in this position?

Also, using the tables, I'm sure it wouldn't be too hard to figure out roughly how much time you need to leave based on where you are positioned (eg. if you know you are at maximum 5 feet below your buddy, you could figure out what difference in time 5 feet makes: it won't be exact, but just use conservative numbers).

The problem with just using tables (at least in the basic way they are taught) is on a multi-level dive they are ridiculously conservative since you are supposed to write down the "maximum depth".

 

[rstofer]

The problem with guessing whether a few feet matters is that it all depends on the depth. The difference in NDL between 60 and 70 feet is 15 minutes. Somewhere in there, a few feet matter.

It would seem to me that the safe thing to do when only one diver has a computer is to use the computer in gauge mode and rely totally on a square profile and dive tables. Yes, it is overly conservative on a multi-level profile. But that's the way it goes.

When both divers have a computer, the more conservative computer controls the dive. That determination must be made on the fly because the algorithms may be different. Basically, at any given point, the minimum RDT (or NDL) is the controlling factor.

Richard