Nitrox?

[tursiops]

IME on Bonaire/Curacao a DM will typically keep to above 20 msw and total dive time will be capped at under 60 minutes, I wouldn't have problem following them for a couple of dives with just the SPG. On Roatan there's swimthroughs etc. that are a different story, but I assume they don't take cruise divers there.

Two dives like that (20m, 60 mins), even on 32% and even with a SI of 60 mins, would violate NDL if one is on tables. That is putting undue trust in the DM to do a multi-level dive and undue faith in the diver that he/she will stay at a depth above the DM at all times. Dangerous diving.

 

[mac66]

Okay.. the basic equipment rentals include a BCD, weights, tank, regulator w/ analog pressure and depth gauges.

The DMs go over the dive profile and safety briefing ahead of time. They have you check the gauges frequently during the dive.

I also wear a watch, (not necessarily a dive watch but good to 100 meters) to keep track of time. I'm pretty cognizant of what's going on.

Dive tables were covered in the class I took, dont remember anything about computers being discussed.

 

[Eric802]

How many of those divers using rented reg sets with attached consoles really know what those computers are telling them? Some have horrible user interfaces. The computer a diver has in his rental gear today may not be the same as the computer in his rental gear tomorrow, so he doesn't have much incentive to learn how to use it. In my opinion, rental computers are as good as useless to most of those divers.

Rental gear is fine, but with your own computer you can learn how to use it once and you're set.

It's pretty much a glorified SPG and timer.

 

[Belzelbub]

How many of those divers using rented reg sets with attached consoles really know what those computers are telling them? Some have horrible user interfaces. The computer a diver has in his rental gear today may not be the same as the computer in his rental gear tomorrow, so he doesn't have much incentive to learn how to use it. In my opinion, rental computers are as good as useless to most of those divers.

Yep. Agreed 100%. A lot of the computers out there today require a pretty good understanding of the manual to know what it's trying to tell you. Some are pretty intuitive, but I'm betting that the computer in a rental console is not going to be one of them.

Two dives like that (20m, 60 mins), even on 32% and even with a SI of 60 mins, would violate NDL if one is on tables. That is putting undue trust in the DM to do a multi-level dive and undue faith in the diver that he/she will stay at a depth above the DM at all times. Dangerous diving.

I don't know why this practice got to be accepted. Maybe accepted isn't the right word, but this practice is at least not unique. It goes against what I was taught, and depending on the dives can be dangerous.

And after 26 dives I'm fairly competent and confident about my abilities.

I was about to jump on this, but then I continued reading...

I do know that I don't know it all and that I have a lot to learn. But I also know that for the type of diving I do and will continue doing, I do okay.

Well stated, and a great attitude to have. 26 dives is not a lot, but as long as you recognize that you don't know everything and continue learning, you should be fine. Always remember, it's up to you to keep you safe. While a DM may be getting paid to do that, the ultimate responsibility lies with you. If the dive plan doesn't seem right, you don't have to do it.

"I was following the Divemaster" would be a stupid epitaph.

 

[mac66]

Yep. Agreed 100%. A lot of the computers out there today require a pretty good understanding of the manual to know what it's trying to tell you. Some are pretty intuitive, but I'm betting that the computer in a rental console is not going to be one of them.

I don't know why this practice got to be accepted. Maybe accepted isn't the right word, but this practice is at least not unique. It goes against what I was taught, and depending on the dives can be dangerous.

I was about to jump on this, but then I continued reading...

Well stated, and a great attitude to have. 26 dives is not a lot, but as long as you recognize that you don't know everything and continue learning, you should be fine. Always remember, it's up to you to keep you safe. While a DM may be getting paid to do that, the ultimate responsibility lies with you. If the dive plan doesn't seem right, you don't have to do it.

"I was following the Divemaster" would be a stupid epitaph.

I appreciate the feedback. So far every dive I've done has been pretty simple and the DMs have always looked after the "old, new guy". I've always felt well cared for but understand that I'm responsible for myself and my own safety.

I really have nothing to prove. Dont need to go deeper or longer. I've enjoyed the short, shallow dives as much as any others. 35 mins at 30-40 feet works for me. Hell, I'm just glad to be able to dive at my age.

Oh...and last week in Roatan on a cruise I talked my younger brothers (one is 65, the other 57) into doing a discovery dive while I did my first dive. Then we dived together on the second dive. They of course struggled with buoyancy but it was fun diving with them. They enjoyed it. I've always been the adventurous one in the family.

 

[Chavodel8en]

OP, while I (and others) previously advised not to take the Nitrox class, Ive got a different thought.

You can use the Nitrox class as an opportunity to go over again the basics of monitoring your NDL (no decompression limits). Basically, the Nitrox class will teach you again how to monitor your NDL, including with the added time at depth allowed by Nitrox. If you actually want to use Nitrox, its very important to understand all the underlying principles, bc Nitrox can add an element of risk (oxygen toxicity), especially once you get beyond about 80 feet of depth.

With a computer its pretty easy to monitor NDL - any computer will have a NDL number (usually the most prominent number - and you dont let it get to 0. You should start reducing your depth as your NDL gets closer to zero. Some dives, especially the shallow dives you describe, you have plenty of NDL time and its not really a problem (although you should still monitor it). Thats basically what you need to know, but it doesnt hurt to know more about how diving/NDL works.

So if you have a depth gauge & a timer, and some tables - you have what you need to monitor your NDL via tables, as long as you know how to use them. However, if you yourself do not have a working depth gauge, I would not necessarily rely on all rental equipment having a depth gauge - they are fairly obsolete now, so are disappearing.

I would think wherever you go could rent a computer as well. Just going ahead and buying a computer and learning to use it may be the best route.

 

[dmaziuk]

Why would one want to monitor one's NDL on a 40-minute dive to 60 feet?

 

[L13]

Rental gear is fine, but with your own computer you can learn how to use it once and you're set.

I always recommend renting your computer from your home shop for a vacation if your are planning to rent. That way you can get familiar with it before you dive.

 

[L13]

Why would one want to monitor one's NDL on a 40-minute dive to 60 feet?

If you didn't plan the dive, you don't know what the time or depth is till you ask the DM after (in the scenario presented). Even if you did, the computer helps you verify it was in fact a 40-minute dive to 60 feet. And if it wasn't, monitor what in fact it was.

 

[dmaziuk]

If you didn't plan the dive, you don't know what the time or depth is till you ask the DM after (in the scenario presented). Even if you did, the computer helps you verify it was in fact a 40-minute dive to 60 feet. And if it wasn't, monitor what in fact it was.

The DM tells you in pre-dive briefing she's going to stay at around 18 msw, and IME they tend to be good at sticking to their planned depth. A momentary max may be 19 or 20, if there's a critter there, but they don't do enough of that to change the fact that the NDL for that dive is about 20 minutes longer than the runtime.

If it's the 2nd dive you may want to make sure your SI was over an hour.