Why do some agencies recommend using a bottom timer instead of a computer

[ams511]

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A ScubaBoard Staff Message...

This thread has been split off from another thread as it was off-topic. Nonetheless, it is interesting in its own right. Marg, SB Senior Moderator

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Buy once, cry once. OP didn't give any more info about long terms plans and what they may or may not want.

on those computers, watch sized computers to me are specific use scenarios vs. good general computers, especially if they're diving locally vs. travel

I am not a technical diver but you are a technical dive instructor, so perhaps you can explain this to me. You recommend a perdix or maybe a petrel, I get that they are the best on the market and do cost less than the top-of-the-line computers from major manufacturers. So I understand the recommendation. However, three technical diving agencies (maybe more), GUE, UTD, and ISE all recommend against purchasing a dive computer and using a simple bottom timer, a function that is built-in to many inexpensive dive computers. So why the difference of opinion?

 

[RayfromTX]

That is an offshoot that is worthy of it's own thread.

 

[ams511]

That is an offshoot that is worthy of it's own thread.

Where do you suggest posting the question to get a real answer? I am curious about this and not looking to troll.

 

[RayfromTX]

Where do you suggest posting the question to get a real answer? I am curious about this and not looking to troll.

Dive computer vs bottom timer and tables
A search turned up many with minor variations on the same theme but starting a new one to answer your specific question seems appropriate and perhaps beneficial to the original poster of this thread who was asking about gear suggestions and wasn't looking to start a fight amongst those with different value systems and priorities. It is a big ocean. Dive and let dive.

 

[Centrals]

Dive computer vs bottom timer and tables

Can't access to it.

 

[dmaziuk]

Where do you suggest posting the question to get a real answer? I am curious about this and not looking to troll.

There's a ratiodeco thread in advanced, I think, that's tangentially related. My take on it is, if you're off your plan for any reason, would you rather try to recalculate your deco on your slate, or carry a computer?

 

[tbone1004]

I am not a technical diver but you are a technical dive instructor, so perhaps you can explain this to me. You recommend a perdix or maybe a petrel, I get that they are the best on the market and do cost less than the top-of-the-line computers from major manufacturers. So I understand the recommendation. However, three technical diving agencies (maybe more), GUE, UTD, and ISE all recommend against purchasing a dive computer and using a simple bottom timer, a function that is built-in to many inexpensive dive computers. So why the difference of opinion?

Their is a LONG history there. Basically the rules that established "no dive computers" came about in a time when you couldn't control the algorithms in the computers, didn't know how to actually figure out what they were doing with any sort of dive planning software at the time, and the hardware was unreliable. UTD and ISE blindly think they can do decompression better than the computers can, which is wrong as proven by the studies UTD paid for where it was found that they not only had longer decompression times, but more markers of decompression stress than the Buhlmann profiles. ISE is kind of in the same camp, but they are basically a spinoff out of GUE like UTD was. Most all GUE divers I know dive computers. You want technical divers to be able to create and execute a plan based off of tables to emphasize how important it is that they follow dive plans, but the computers are going to always do it better. I would not be surprised if GUE changed their official stance on computers in the next year or two. Too many of their divers and instructors are using them for them to ignore it. Now that we have reliable computers that can be set to the same parameters that they use in decoplanner, it doesn't make any sense not to.
NAUI also forces uses of tables in their tec courses.

 

[tomfcrist]

There is nothing wrong with teaching timers and tables. When I dive OC, I never take 2 computers. I have a plan in my wetnotes to follow if needed and a$10 Casio on my wrist to backup my predator.

CCR I have a petrel controller, and a my Predator as a backup.

That being said neither the $10 Casio, nor the shearwater have ever failed me.

One could understandably justify wearing 2 shearwaters and not bothering with written dive plans.

 

[rongoodman]

Jablonski's "Baker Dozen for not using a dive computer" is at least 15 years old. Technology has advanced a lot since it was written.

 

[Chris H]

I started my OC tech diving with tables and a bottom timer. It works just fine. I now have a CCR with a Petrel 2 attached to it and it works just fine too. It works well enough that I bought a backup Petrel. That said, the agencies that aren't advocating using computers sometimes take the "Thinking diver" stand on the argument. They are trying to get you to think about what you are doing, and why you are doing it, vs blindly following your computer. For example, I once did a dive with a diver who couldn't figure out how to switch gas on his computer. He physically switched gas to a deco gas, but decided not to get out of the water until his computer told him it was OK instead of thinking what his gas switch meant to the deco profile. We were in the water 20+minutes longer than we needed to be, which wasn't an issue at the time, but could have been.