Diving against time or air limits normally?

[RonFrank]

Any type of diver can end a dive for any reason at any time. It is hardly a technical requirement, in fact quite the opposite.

I generally dive until NDL, or I get cold, bored, etc.

On a shallow dive in FL (25'ish depth), it is hardly unheard of to go two hours if shore diving, and end it only because 2 hours is plenty of time underwater. On a boat that will never happen as they want folks back in the boat after one hour as they have schedules to keep. I find one hour on most shallow reefs is adequate.

For deeper dives, it will be NDL based. For example diving Boyton (FL), the depths can be 100' at times and even diving Nitrox it's difficult to get bottom times of more than 50 minutes without going into NDL.

I once was partnered with a couple who could not get 30 minutes on a 80 at 25' before they were low on air. Not problem, I would return them to the boat, and go back down for the rest of the time solo.

As a new diver, you will suck air. Give it time, and you likely will improve. The main goal is SAFETY and then enjoyment.

 

[Sas]

Against time limits or my ability to tolerate the cold. Almost never air.

 

[Damselfish]

it's going to vary. Sometimes there will be a time limit, sometimes not. Sometimes people will dive more or less in a group (especially on a drift dive) and come up together at a specified time or depending on people's air. In the case of a group there may be a plan for people to surface in 2 groups or with their buddies as they need to if that works in the situation, in order to allow people better on air to stay down longer. Often you won't be diving with a group at all if you don't want and will do whatever works for you.

People do realize that most new divers will use air faster. Don't stress about it (especiually before you've even started), you'll just make things worse. This phase passes soon enough as you relax more and get your weights and buoyancy dialed in. One thing you can do to conserve air is to watch your depth and dive a bit shallower than the group rather than deeper, this is easy to do on many dives without missing anything or being too far away. Another is to avoid situations where you'd be doing deeper dives in general until your air consumption gets better, which is a good idea anyway. That will help extend your dive time.

 

[TMHeimer]

For me, this in general: "shallow" down to 60-70 feet I'm usually limited by air. 80-90 feet by either air (gas) or NDL (time). Deeper than that by NDL, as with most people. Of course there are variables. 70-80 feet--don't know where I'd put that.

 

[udtfire]

plan best for time but as a new dive worry about gas watch it all the time and figuar you sac rate
then exit water at 500 psi
know where exit is at 1000 psi
turn the dive at 1500
start with 3000 psi
watch your buddy, communicate, relax enjoy

 

[TSandM]

In the beginning, you really don't know what to use to plan. Gas will be the limiting factor, but you don't know how long it will last. You need to get a couple of dives under your belt to begin to understand that -- AND it varies with depth. The deeper the dive, the faster you go through your air (you will learn this in class).

As you become more experienced, you'll figure out how long your gas will last, and eventually, it may last long enough that some other factor (whether that's fatigue, cold, decompression, or the need to urinate will depend on where you are diving) will end your dive.

For me, in Puget Sound, it's cold. Diving 32% Nitrox, as I do, NDLs rarely are relevant, and I NEVER get low on gas, but in winter, sub-50 water, 45 to 60 minutes is my absolute max.

In the caves, where the water is warm and the depths are shallow, I often turn dives on "I swam in over an hour, I have to swim over an hour back out".

 

[jmasin]

For shallow dives like shore dives at 20-25' it is food Tummy growls first.

For other dives, as a large-lunged athletic man it is always air limited, much to the chagrin of my small-lunged non-athletic wife

With experience I've gotten closer to her consumption but I'll never reach it. It's a shame that most of the air in my tank is wasted, but it is a fact of life as a 6'2" guy with decent lung capacity...

 

[diver 85]

If you are going to start a class soon,I am assuming you are not certified, just relax and listen to the instructor.Don't worry about what could happen down the road.Enjoy the class ask your instructor any questions you might have throughout the entire class.Diving is a fun activity don't burden yourself at this point with any uneccesary "worrying".All things will fall into place as you start to learn,all questions will probably be answered by your instructor and if you have more questions ask him thats his job .Go into the class with the idea of having fun and enjoying yourself.

Great advice here---------OP, never put a cart before a horse--sometimes it'll go backwards....


But, ----------in general, air calls my dives...

 

[herbdb]

I will never match my two sons on gas usage. My solution is that for our local diving, I dive 120's and they use 80's. This keeps everyone happy and makes for longer dives together.

 

[LivBlue]

Thanks for help guys, it was just something while reading my materials that occurred to me. For obvious reasons the book cant give numbers or even great examples of dives. Having no working knowledge left me trying to imagine what an operation would be telling me as we pulled up to a spot about getting back at a certain time or if I'd be making a plan that was built more on staying down till air was the limiting factor. I enjoyed reading the examples.