How to plan second dive of the day using a computer

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The problem is defining the term "superior". You've gotten a bunch of opinions here, from people who plan dives to people who don't do any planning at all. You've heard from folks who have discovered that computers (like tables, actually) can vary quite a bit in what they indicate for no-deco limits and how they penalize or reward you for time spent at intermediate depths. You've heard from folks who think that teaching tables gives divers a better understanding of nitrogen dynamics, and from folks who think that spending the time to understand compartment readouts (if your computer even has them) gives a better grasp of the idea.

In the end, there are two things: What keeps the incidence of DCS the lowest, and what gives divers the best intellectual understanding of the subject. The two are not necessarily related. DCS incidence is very low, and most of the cases are due to people egregiously violating either NDL time or ascent rate -- this is regardless of the table or computer algorithm being used. Deaths in recreational diving are RARELY due to the bends -- they are far more frequently due to embolism from panic or out-of-gas situations. So I think it is fair to say that, no matter what your understanding of your compression-management system is, the system works.

For those of us who want to have a better grasp of what the system is DOING, neither studying tables nor looking at computer readouts is going to do that, because both imply that we actually understand what is happening in the body . . . and we don't. To get a thorough picture of what your tables or computer are doing, you need to understand the basis for the table or readouts, and what the unknowns are. That's where a book like Deco for Divers comes in, or the GUE DVD, The Mysterious Malady. There are also a lot of resources on line, like Erik Baker's paper, "Understanding M-values", which is available on many sites.
 
"The whole idea is to know how long you can remain at your planned depth before you hit deco. Oh yeah, it is important to know this BEFORE you splash..."

Well, your computer will also tell you while you are in the water how long you have at your current depth/time, etc. Not saying you shouldn't plan your dive and dive your plan. Just pointing out that this information will be displayed to you realtime based on where you are.
 
"The whole idea is to know how long you can remain at your planned depth before you hit deco. Oh yeah, it is important to know this BEFORE you splash..."

Well, your computer will also tell you while you are in the water how long you have at your current depth/time, etc. Not saying you shouldn't plan your dive and dive your plan. Just pointing out that this information will be displayed to you realtime based on where you are.


I should have finished the sentence just to avoid confusion with where I was going with it. How about:

"Oh yeah, it is important to know this BEFORE you splash so that you can enter the water with a valid gas plan. (-for those that do such things)"
 
The reason was we could see that we were spending too much time and effort on dive tables, and not preparing our student for real life diving.
Today almost all rec. divers use computers. We have required dive computers on our trips since 1990.

Do you think you would have been better off learning how to use a dive computer from day one?

It seems to me that it would be much safer to use dive computers right off the bat. They are simpler, not prone to user error, and display much more usable information. Has PADI and the other associations just not implemented it because the technology is just now starting to be priced more affordable?
 
Has PADI and the other associations just not implemented it because the technology is just now starting to be priced more affordable?

If I remember correctly, PADI no longer requires the teaching of tables but instructors can include it if they want. Several of the instructors I know don't teach them any longer.
 
If I remember correctly, PADI no longer requires the teaching of tables but instructors can include it if they want. Several of the instructors I know don't teach them any longer.

I know when I did my OW they tested and I had a referral in the Bahamas and they tested on it as well. So, there are two PADI shops requiring it, at least, to get your c-card.
 
So what do I do to "plan" the dive? Nothing really. Basically we all gear up and off we go watching our computers. I quit logging dives when I reached 500 so I do have a bit of experience and pretty much understand how much air I typically use on a dive. I don't think I have ever seen anyone, myself included, actually take a computer, go to the planning stage before the dive, and run through a program that tells you how much time you will have at 100 ft. Do I really need to know before I jump in how much time I have at 100ft? If I want to know that I just look at my computer when I reach 100ft.

It's one thing if your doing the same dives on the same mix day after day to know your time limits, it's a complete other thing when you may be diving air for example and others are diving nitrox. A good example would be the drift diving we do here up in jupiter. Let's say you had two tanks already filled with air that you were going to use for some shore diving and someone calls to do a few 70-80 ft drift dives in jupiter. Rent tanks or know what your doing with your dive planning if using air. This is one feature I actually do use a fair amount. In my example after a 70-80 ft drift dive at around forty minutes on air your buddies are anxious to get on to dive two after a shortened surface interval. Just an example but they may have 40 minutes allowed on the next dive to the same depth and you may have 20 minutes. At that point you need to make the decision to even bother with the dive or if you can talk them in to waiting a bit. It's a very nice feature and there are many situations were it can be helpful in making decisions on your next dive.
 
I should have finished the sentence just to avoid confusion with where I was going with it. How about:

"Oh yeah, it is important to know this BEFORE you splash so that you can enter the water with a valid gas plan. (-for those that do such things)"

I guess we'll let you slide... :wink:
 
The real thing you need to know is the residual nitrogen itself. And even that is a second-best piece of data, because you really need to know the amount of nitrogen in each of the 16 compartments.
As TSandM already stated we do not KNOW very much about what really happens in our body during decompression.
The compartments (some algorithms use 8, some 12, some 14 some 16) are THEORETICAL, too.
We do not even KNOW what the basic mechanisms of DCS - the problem all dive computers and dive tables try to avoid - are.
 
https://www.shearwater.com/products/swift/

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