Watch Sized Or "full" Sized Computer ?

[RainPilot]

My 0.02 worth: You mentioned that you are 22, if you are serious about your diving then its worth considering where you may end up e.g. tech, deco, multi-gas etc etc. This plays a role in deciding which computer will stay with you vs buying one now and ending up with a few computers later on.

I would also ensure that whichever one you choose should have easily available, user replaceable batteries. Many folks have found themselves high and dry a few years on when the manufacturer for whatever reason stops support. This is obviously simpler using a larger computer with AA or AAA batteries, but if considering a watch battery make sure the unit takes the CR batteries

 

[victorzamora]

@victorzamora : Why do you recommend turning off deep stop ? Very useful comment though, thanks !

P.S : Not an English native, hope I'm doing fine writing all those words.

Your English is very good. I'd say as good as some native English speakers.

As for deep stops, it's the same reason I recommend against the Mares/Suunto style algorithms. There are a few theories out there for calculating decompression since we can't measure anything in our body (like Nitrogen loading) directly, mathematical models are as close as we can get for now. Different models have different approaches to how to verify you're "safe." The Mares/Suunto algorithms are based on "bubble models" that are all about preventing bubble formation. The idea behind a deep stop is that if you stop while relatively deep, you can give your body a better chance at not producing bubbles. The problem is that recent experiments in the military diving world (by the top decompression physiologists in the world) have unanimously disproven deep stops to be good. Almost all divers get bubbles on every dive, and deep stops do more harm by making you stay deeper and absorb more nitrogen....so the theory behind the model and behind the deep stops were proven to be wrong. In recreational diving it's not a big deal....but the point is the same.

 

[KeithG]

If you shop carefully your first purchase should last many yrs.
I bought my first computer Uwatec Aladin(air only) in 1996 and the nitrox version a yr later. The air only computer died last yr but the nitrox one is still doing fine.

Died? What you you mean? Died malfunctioning or Died dead battery?

Dead battery died units can be resurrected. I do this routinely as I have accumulated a large handful of Aladins. I have never had an Uwatec computer malfunction. They just ran out of juice.

Going diving next week with a bunch of 21 year old computers...They are youngsters (compared to me...)

 

[dmaziuk]

In recreational diving [deep stops] not a big deal....but the point is the same.

Last I looked the staunchest proponents of deep stops said they have no use in recreational diving whatsoever. And that the equivalent use of GF low is at best "undefined" on recreational dive profiles (that one might've been @RonR, I forget).

Now, echoing the other posts, if OP is planning to go tech, then they have good reasons to avoid any of the above, save up and buy a perdix/ostc/tx1. Which would also take the deep stop issue out of the picture.

 

[Jax]

Last I looked the staunchest proponents of deep stops said they have no use in recreational diving whatsoever. And that the equivalent use of GF low is at best "undefined" on recreational dive profiles (that one might've been @RonR, I forget).

Now, echoing the other posts, if OP is planning to go tech, then they have good reasons to avoid any of the above, save up and buy a perdix/ostc/tx1. Which would also take the deep stop issue out of the picture.

I beg to differ.

I suffered from sub-clinical DCS fatigue to the point that I wanted to give up diving. Doing a half-depth stop made all the difference in the world.

 

[victorzamora]

Last I looked the staunchest proponents of deep stops said they have no use in recreational diving whatsoever. And that the equivalent use of GF low is at best "undefined" on recreational dive profiles (that one might've been @RonR, I forget).

I actually meant to imply that bubble models (the theory behind the Suunto and Mares models and the theory behind deep stops) have been recently having multiple failures. I think deep stops, even in rec diving, have been conclusively proven as "not good."

Now, echoing the other posts, if OP is planning to go tech, then they have good reasons to avoid any of the above, save up and buy a perdix/ostc/tx1. Which would also take the deep stop issue out of the picture.

This, I agree with. If there's a plan for Tech then a Perdix (or similar) would make more sense. I think the Tx1 is too much money for what it is, but that's a different discussion.

I beg to differ.

I suffered from sub-clinical DCS fatigue to the point that I wanted to give up diving. Doing a half-depth stop made all the difference in the world.

Jax, I'm glad they help you. However, this contradicts the findings of several recent studies. Also, my understanding is that half-depth stops weren't recommended.....it was half-ata stops, which are much shallower. I know you know this, but as a quick example at 99ft=4ata: half-depth is 50ft while half-ata is 33ft. The findings, however, are pretty clear that pushing up your deepest stops and flattening that curve out is, statistically, the most "efficient" manner in off-gassing safely.

Regardless of what findings say, I'm glad it's working for you as that's really what matters. They're finding that hydration matters much less than once thought, but I know that being well-hydrated before a dive gets me out of the water feeling much less tired. I'm struggling to phrase this in a way that doesn't sound sarcastic, as I mean it honestly: What works best for you is what works best, period. That's one thing I like about Buhlmann, I can shape my deco curve to whatever suits me best. Mine has been moving my GF-Lo higher.

 

[dmaziuk]

I beg to differ.

I suffered from sub-clinical DCS fatigue to the point that I wanted to give up diving. Doing a half-depth stop made all the difference in the world.

That doesn't in any way contradict what I said. What I said was, however, not entirely correct: re-reading Alert Diver | Deep Stops it appears one out of 5 experts didn't outright say they're pointless on recreational dives and did, indeed, advocate a half-depth stop. So I was only 80% right.

Should recreational divers staying within no-decompression limits be concerned about deep stops?

Mitchell: No. There is insufficient data to justify a deep stop approach in recreational, no-decompression diving. Divers should, however, pay careful attention to ascent rates, and the imposition of shallow safety stops is still considered beneficial.

Southerland: Recreational divers should be aware of the issue. If sufficient evidence becomes available, then a diver might be better off just upgrading the dive computer with a newer algorithm.

Gutvik: No. The recommended safety stop and a controlled, slow ascent rate are adequate for performing safe no-decompression dives. These dives will normally be either too shallow to consider deeper stop depths or too short for the deep stops to have an effect.

Bennett: There is no more reason for concern about deep stops than for the widely accepted shallow safety stop. Both were developed based on the reduction of bubbles in the blood vessels seen in research studies. The research on the deep stop is, in fact, more extensive and is based also on actual recreational dives. The deep stop at half the depth for 2.5 minutes significantly reduces not only bubbles, but also the critical gas supersaturation in the "fast" tissue compartments (like the spinal cord's 13.5 minutes) without increasing the "slow" compartments usually related to limb pain. More recent research is concerned with the damaging effects of bubbles on the endothelial lining of blood vessels. Reduction of such bubbles will prevent this.

Doolette: Recreational diving within no-decompression limits conducted with a shallow safety stop has a good safety record. There is insufficient evidence to suggest a deep stop offers any advantage.

Meet Our Panel

Peter B. Bennett, Ph.D., D.Sc., is executive director of the Undersea and Hyperbaric Medical Society. A former tenured professor at the Duke University Medical Center department of anesthesiology and director of the Duke Center for Hyperbaric Medicine and Environmental Physiology, he founded Divers Alert Network in 1980.

David Doolette, Ph.D., is a research physiologist at the U.S. Navy Experimental Diving Unit, responsible for development and testing of decompression procedures.

Christian Gutvik has a master's degree in engineering cybernetics with specialization in mathematical modeling. He works with the Baromedical and Environmental Physiology Group at the Norwegian University of Science and Technology, where he is the main modeler of Copernicus, a decompression model based on ultrasonic detection of vascular bubbles.

Simon Mitchell, BHB, MBChB, DipDHM, DipOccMed, Ph.D., is an avid technical diver and a physician specializing in occupational medicine, hyperbaric medicine and anesthesiology. He received a doctorate for his work on neuroprotection from embolic brain injury.

David Southerland, M.D. is a captain in the U.S. Navy Medical Corps and the senior medical officer for Naval Diving and Salvage Training.

 

[Centrals]

Died? What you you mean? Died malfunctioning or Died dead battery?

Dead battery died units can be resurrected. I do this routinely as I have accumulated a large handful of Aladins. I have never had an Uwatec computer malfunction. They just ran out of juice.

Going diving next week with a bunch of 21 year old computers...They are youngsters (compared to me...)

Not malfunctioning or ran out of juice. But there was one big black patch appeared on the screen covering certain critical area as I switched on the unit for the first time after a while.

 

[Jax]

Jax, I'm glad they help you. However, this contradicts the findings of several recent studies. Also, my understanding is that half-depth stops weren't recommended.....it was half-ata stops, which are much shallower. I know you know this, but as a quick example at 99ft=4ata: half-depth is 50ft while half-ata is 33ft. The findings, however, are pretty clear that pushing up your deepest stops and flattening that curve out is, statistically, the most "efficient" manner in off-gassing safely.

That is the first I have heard of this "half-ATA" as a deep stop. I learned of the deep stop reading about Pyle. I use Uwatecs which have something called a Position Dependent Intermediate Stop (PDIS) - it tracks your depth and adjusts a 2-minute deep stop accordingly.

Regardless of what findings say, I'm glad it's working for you as that's really what matters. They're finding that hydration matters much less than once thought, but I know that being well-hydrated before a dive gets me out of the water feeling much less tired. I'm struggling to phrase this in a way that doesn't sound sarcastic, as I mean it honestly: What works best for you is what works best, period. That's one thing I like about Buhlmann, I can shape my deco curve to whatever suits me best. Mine has been moving my GF-Lo higher.

I support this 100%. I prefer VPM-B, though.

 

[boulderjohn]

That doesn't in any way contradict what I said. What I said was, however, not entirely correct: re-reading Alert Diver | Deep Stops it appears one out of 5 experts didn't outright say they're pointless on recreational dives and did, indeed, advocate a half-depth stop. So I was only 80% right.

The research on deep stops Victor referenced was done AFTER this round table discussion. It was directed by one of the people in the discussion--Dr. David Doolette. Doolette and Mitchell participated quite actively in a discussion on this topic recently on ScubaBoard, and that discussion has recently been resurrected and is active again.