What is an optimal dive watch for dive master?

[charlier]

In summary - The Suunto Algorithm is fine for Rec diving and guiding
Get something easy to read
Something easy to operate
Don't worry about built in compass - buy an normal wrist one
DO make sure it has a timer or you have an additional timing device

@Diving Dubai is on the mark - Suunto's are fine for recreations diving as guiding. As a guide, I usually carry a spare computer as well and strap it on my harness.

edit: Full disclosure, I personally use a Perdix AI. Regardless of my personal choice, the Sunnto's are still a good dive computer.

 

[dmaziuk]

What about the statement that both models are completely different do you deem "wrong". The Buhlmann (sic) model is an dissolved gas model based on Haldanes work, whereas RGBM, like VPM, attempts to accommodate bubbles in a dual phase approach.

VPM For Dummies

In terms of the algorithm in Comp. Sci. sense, it's the same model, the difference is ZHL+GF modifies the M-value by a fixed number (Gradient Factor) whereas bubble models modify it by a variable output of the "bubble" formula. RGBM supposedly uses a different formula here, but it's still half a dozen of one vs. six of the other: you have an M-value, you modify it by a number calculated using one formula or another. (A Gradient Factor is a formula too, it just produces the same fixed constant all the time.)

Still, Suunto doesn't even use RGBM.

Also what is wrong with the statement that both models, produce safe recreational dive profiles?

What's wrong is "safe" implies a binary safe - unsafe dichotomy. In some ways it is, like when you surface not bent, your model was 100% safe. This time.

In reality the M-value denotes a statistical guesstimate of the risk of developing clinical DCS. M-value programmed into ZHL-16 model is "safe", yet most divers choose to reduce it to 80% or less by using gradient factors. Gotta wonder why, if GF 100 was perfectly safe to begin with -- maybe they want to cut their precious NDLs short?

 

[KenGordon]

Modern evidence (2011 NEDU study) points to the oldest model-based algorithm in use, Buhlmann with flat gradient factors, usually known as ZHL-16, being the best

They did not test any Buhlmann model in the NEDU deep stops study. They tested one dissolved gas model, but with linear off gassing, against a bubble model. But neither of those models are in common use amoung people diving for fun.

That study helps decompression divers decide on some things but doesn’t matter to anyone guiding holiday no stop divers.

 

[stuartv]

If you're going to be leading customers on dives that they paid for, I would get a very liberal computer, or a Perdix.

If I was your customer, paying you to lead me on a dive, and I had to end my dive early because your computer was about to put you into deco (because it was more conservative than mine), I would not be a happy customer.

If you think "well, if my customer has more NDL, then I'll just stay down and go into deco," then there are 2 issues. One, are you trained for deco? If you are not, then as a dive professional (which a DIve Master is), you should never exceed your training or certification limits - so, do not go into deco. A dive pro should be a good role model, in that regard (as well as adhering to agency standards that require such). And, two, if you go into deco, you put yourself in the position of not being able to surface immediately, if needed. When being paid to lead other divers on NDL dives, that is not appropriate, in my book. Also, it puts you in the position of POSSIBLY causing your computer to lock you out, impairing your ability to safely lead subsequent dives.

In the case of a pro, leading people on NDL dives, I feel like a Shearwater Perdix is the best option. You can adjust the gradient factors to match (roughly) the most liberal computers and the most conservative. And, it will never lock you out.

If you are just going to be a Dive Master assisting an Open Water instructor with classes, then I don't think it really matters much and you would probably be fine with the cheapest computer you can get. Personally, I have been considering getting a cheap console/computer to attach to a single tank reg set that I would dedicate just for use when teaching. I strongly prefer a wrist computer when actually diving for fun (or my own practice). But, the extra step of donning/doffing a wrist computer when I'm teaching in the pool or doing checkout dives in the quarry seems like a nuisance sometimes. Particularly since I wear a wetsuit even in the pool, so donning/doffing of the computer happens more often than if I just wore a rash guard. E.g. I have to doff then re-don my computer every time I need to go for a pee break.

 

[dmaziuk]

If I was your customer, paying you to lead me on a dive, and I had to end my dive early because your computer was about to put you into deco (because it was more conservative than mine), I would not be a happy customer.

Have you actually been on a dive where a paid dive master got everyone out of the water because the dive master's computer ran out of NDL? Or even have a friend who knows someone who once been on a boat with someone who said that once happened to a mate of theirs?

 

[Diving Dubai]

If I was your customer, paying you to lead me on a dive, and I had to end my dive early because your computer was about to put you into deco (because it was more conservative than mine), I would not be a happy customer

An how much difference in NDL would you accept? 1 min 5 mins?

What happens when some of your group are on air and others are on Eanx?

I guide groups to the most conservative computer, so if you're in a group and someone runs up their NDL, up we go.

No-one here guides on a Perdix, and most own one or two for tec diving

 

[walkonmars]

I do not recommend any Suunto at the moment.
I have a Petrel and use it in "Tec" mode all the time (even though I am recreational solo diver).
There is a screen that shows you the gas loading levels of all 16 model tissue compartments and you can watch the bar graph change as you ascend and descend or wait at your deco and safety stops. Not a single dive goes by without me checking this screen. You can better explain to your student's tissue saturation and loading (or approximate since you are diving together) levels and let them better understand why they are better off to safety stop, deco stop or ascend more conservatively. Perdix users need to confirm that this screen also exists on the Perdix, as well. You have options to add AI later if you choose and the plan mode while on a surface interval is super easy to bring on and show. You can adjust conservatism but the least conservative may sometimes be more conservative than another computer (others to confirm).
I used to have Suunto Vytek and Zoop and although they lasted more than 5 years, when they stopped working (faulty depth sensor) I didn't get good support or sympathy from Suunto. They wanted me to buy a new computer with some discount but not large enough of a discount for me to use a Suunto ever again.

 

[Magnus Lundstedt]

Still, Suunto doesn't even use RGBM.

It is true that the Suunto-RGBM is not relay an RGBM, but the Suunto Fused RGBM is acctualy a combination of the S-RGBM in shallow water and a real RGBM when going deeper. The S-FRGBM is used in Eon models.

 

[dmaziuk]

It is true that the Suunto-RGBM is not relay an RGBM

Are you Dr. Bruce Weinke in disguise and/or do you work for Suunto? Because otherwise I don't quite get how you know those things: both "really RGBM" and "Suunto not RGBM". Care to provide a cite or something? Perhaps point to a manual for a Suunto computer -- any Suunto computer -- where it says it's not running RGBM?

 

[Magnus Lundstedt]

Are you Dr. Bruce Weinke in disguise and/or do you work for Suunto? Because otherwise I don't quite get how you know those things: both "really RGBM" and "Suunto not RGBM". Care to provide a cite or something? Perhaps point to a manual for a Suunto computer -- any Suunto computer -- where it says it's not running RGBM?

I maybe used some word that can get missunderstoud, the S-RGBM is an approximation and simplificcation of the RGBM that had been added extra fluff. I should have said that it is not a full RGBM instead of not really. Sorry for that.

The Suunto T-RGBM are a full RGBM and the Fused RGBM is a combination of the previous.


The big difference is that the S-RGBM uses simplification inside set parameters to save cpu-cycles.





Listen to Dr. Bruce Weinke explain "Why use S-RGBM instaed of full RGBM"