Does not compute but should I ?

Most of my diving is double dive boat diving usually a first dive of 25-30 mtr first up followed by a second dive of about 10 -15 mtr.
My question is would a dive computer be of any use to me. We have a good working knowledge of the dive tables and we do use them. My understanding of computers is that they are good for multi dives and for instructor's. Would it be worth looking into or not?

Hi Aqua Prop, welcome to the board. The issue of computer use is one of great debate. Some will argue that a dive computer simplifies dive information, is easier to use and provides a margin of safety due to their conservative nature. Others will argue that a good working knowledge of the dive tables and basic instrumentation is all that is necessary. The main arguement I see against computers is that they "rot your brain" by displacing your knowledge of the tables. If you don't use them you won't remember them before long, right? Other arguements include the conservative nature of the computer and complacency due to relying on a computer.
I prefer to use basic instrumentation and the tables. There is nothing that a computer can do that I can't do with a set of tables, a depth gauge, bottom timer and a little brain power.
I guess the real question is weather or not you see any real need for a computer. Seeing as how you typed this thread, you have been doing alright with tables so far, right?

Next best thing to a mask if you ask me. But don't forget your tables either..

Search this board.. This was talked about before.

If you simply drop to some depth, stay there and return to the surface, then tables are fine. But if your dives are more varied, then using tables and getting max bottom time is a lot more difficult. I did a dive the other week that violated the heck out of any table but was in fact fine. We were diving in a cavern and dropped to about 35ft where my buddy and myself had some equalizing problems. We had to linger at that depth for a several minutes while our ears cleared, we then proceeded to about 95ft for several minutes and finally returned to 20ft for at least 30 minutes. We had plenty of gas so we decided to hang around at that depth and do safety drills. The max time by the tables is in the 20 minute range, our actual time was 59 minutes but at no time did we go into deco, did not even get close. Had we been using tables only, our dive would have been cut by 2/3s. These multi level dives are typical for me.

I don't buy the "rot your brain" argument. No doubt there are "divers" who would totally forget the tables but I suspect they will anyway....you know--jump in, follow the guy next to you style diving. These "divers" are not going to use the tables no matter, at least a computer MIGHT help keep them safe. Then there are others, myself included, that use a computers but I refer to the tables as well. I know the NDL times and can use tables if I need to. Add NITROX to the equation and the computer add a lot more value.

herman once bubbled...
Had we been using tables only, our dive would have been cut by 2/3s. These multi level dives are typical for me.

Click to expand...

I see the above statement as proof that computers do indeed rot your brain. Had your brain been free of rot you might have realized that diving the same profile results in the same inert gas load whether you are using a dive computer or not.

All of our dives are multilevel... even the ones where the bottom is at a constant depth.

I fin this an extremely interesting subject (if it isn't an argument). There are few things in the world that interest me more than dive planning. I certainly like the idea of being free of computers and for that matter tables (like the WKPP). The later I don't dare actually do but rather just study?.

For those not familiar UP and other GUE trained divers refer to a computer being more conservative because they use a methode some refer to as profiling. The rest of the world is tought to use their MAX depth to calculate a dive, which is why most can't use tables for a multi-level dive without a severe penalty. Divers brains are not being rotted by computers but rather they are not learning this methode that as far as I can tell is only being tought by GUE. I have dived with and talked to several GUE trained divers extensively about this methode. My understanding is that, with a knowlege of the profile you actually dive you simply decide what depth to use for calculation or I guess you could calculate the dive as a multilevel using the tables. Do you use an average depth? Something greater for added safety? or something less if you feel lucky? I guess it's a matter of experience and knowing what you can get away with. Another question I have is which tables do you use? The $64 point that I made when discussing this is that none of the models the tables are based on use average depth or even average presure. That just isn't the way the math works. I'd have to give it some thought but I guess an average area under the half time curves would approximate normal table results. Of course I realize that the model the table is based on is just that a model and doesn't directly represent what goes on in the body. On the other hand some of these models have been tested extensively. If you use an average depth or anything rather than the MAX depth you are then using an untested (other than by you) model.

I'm not saying it doesn't work because divers do it but it seems to me there is alot of guessing. I would be especially concerned about someone on vacation doing several dives per day who may be pushing things a bit anyway. I would be interested to know hoe guessing? or using the table in a mannor it wasn't designed to be used works when getting closer to the edge (for lack of a better term.

As always I would love to hash this over more.

"I see the above statement as proof that computers do indeed rot your brain. Had your brain been free of rot you might have realized that diving the same profile results in the same inert gas load whether you are using a dive computer or not."

I fully realize that my computed gas loading is uneffected by the method of computation be it by tables, computer program or dive computer. So Pug, are you telling me that you calculate the exact bottom time remaining, nitrogen loading, O2 loading and any possible deco time on the fly in your head during a dive? I have no doubt that you can do a multilevel dive plan on the surface (I can, even with my rotten brain ) but how do you handle a change in the dive plan at depth.

A dive computer is nice in that you can download the dive profile to a computer to help with your logging, and it also combines a few gauges into one convenient location. If the dive tables are working fine for you and you aren't trying to squeeze out extra bottom time, then the computer will really only be an expensive depth/bottom timer for you. If you want to squeeze out some extra bottom time, the computer can do that as it isn't limited to counting your entire time at the lowest depth of the dive, like the tables are.

I am not an expert on this and wouldn't attempt to explain it here anyway... consider my above comments a teaser to get you to take a GUE class and get the inside scoop from them.

But the computer(and advertising!) leads us to believe it is.
Plan your dive, dive your plan.
Relying on computer commands underwater pales to knowing in your head what to do. Technology should enhance our experiences, not drive them.
Herman, in your case, all the time you spent at 20 ft. at the end of your dive, that's called deco time, not bottom time in my book.
Aquaprop, if you are using tables and planning dives now, you are ahead of the game. Ask yourself, do you trust your own decisions, if you do, why get a computer?