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I guess the thing that puzzles me is this: We have a scenario here (4 days x 24 dives) that your dive computer will let you do, but will get you bent, and nobody seems to have a definitive answer for. If 4x24 is bad, and 4x15 is okay, then where is the line?
Nobody can ever guarantee that you can't get bent. Diving 4-5 hours a day, at depths greater than 25-30' (8-10m) and you can most certainly get bent.
Diving 4 times or 5 times a day, depending on the profiles isn't crazy aggressive. It can be done, and IS done all the time - especially on liveaboards. 5 dives a day is the schedule...
I frequently do 5+ hours a day in the water, it depends on how deep though. Maybe I do it in 2 dives instead of 5 though. But the bottom time is similar... yes?
If you don't dive "to the limit" every time, you can easily do 5-6 dives a day. Just diving your computer without a lot of complicated 4 day plans.
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I have often heard "skip the third day" on liveaboards. I'm not usually willing to do that in the absence of some indication (from my body) that I'm pushing my personal limits, but I do dial it back to a 2-dive day at some point around mid-week.
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Everything I post is an opinion; I do not pretend to have any facts to offer. Much of what is posted here is in jest, and is not intended to be taken seriously. The sarcasm is often so subtle it's hard to detect.
The thing with liveaboards and the rhythm of the dive day is that there are generally two deep dives early in the day and then a series of progressively shallower ones. I have, unfortunately, just been dealing with one of my divers having got bent (Type 1) on a liveaboard here in Thailand after only a day and a half of diving (he's done with his chamber treatments and is flying home tomorrow). The chamber tech (who is also a dive pro) and I sat with him for a while and discussed what he can do to attenuate future problems (the doc has indicated that he will be cleared for future diving with no restrictions).
Now, here in Thailand we have "only" four dives a day on our liveaboards, mainly because our dives are rather deep, on average--significantly deeper than the dives in the Caribbean in my experience--and our divers simply get too short on bottom time by the end of three dives to do anything but a shallow and short-duration sunset/night dive to round off the day. My diver apparently actually got bent on the first day, when he thinks back on his symptoms in hindsight, but really only got recognizably symptomatic after his 6th dive--his second deep dive of the second day.
The upshot is that a "skip the third dive" or "skip the third day" rule is perhaps comforting, but may not actually work. If a diver were to follow that rule here, s/he'd have two deep dives and skip the shallower afternoon dive. What can help here is skipping one of the two morning deep dives and cutting down to "just" three dives a day. What can also help is diving nitrox on air tables (without violating the MOD, of course). Long surface intervals help (which is what you get when you skip that second deep dive of the day). And, clearly, skipping a day of diving to offgas can also be a big help. Because on a liveaboard you will have to make hard choices about what to skip, it might be more workable, as Vlad proposes, is to cut down to two dives mid-week, skipping not only a deep dive on the two-dive day, but also the night dive the night before, making that a three-dive day rather than four, especially if it's not a really thrilling one (most of our night dives here aren't that great, and I'd happily skip 75% of them).
I personally from my limited expierience can not imagine doing 7 dives in one day for multiple days in a row, especially on air. And why 40 minute dives, when you can do less dives for longer, therefore not having to mess with your dive rig setup so many times. Personally I think you should get enriched air certified before you even think about running such a dive profile, because with that much nitrogen loading I think I would be so tired at the end of the day, I wouldnt make it back into the water the following day. Hows your health, and physical fitness level?
The most intense diving I ever did in a short time was in the Maldives back in 1998 and from my log book the profiles were as follows:
All dives on Air.
Day 1
In: 15:09 Out: 16:01 Time: 0:52 Note: Check out dive
In: 16:40 Out: 17:40 Time: 1:00 Total Time: 1:52
Day 2
In: 07:11 Out: 07;41 Time: 0:30 Total Time: 2:22
In: 10:40 Out: 11:28 Time: 0:48 Total Time: 3:10
In: 15:16 Out: 16:06 Time: 0:50 Total Time: 4:00
In: 17:06 Out: 17:36 Time: 0:30 Total Time: 4:30
In: 18:54 Out: 19:40 Time: 0:46 Total Time: 5:16
Day 3
In: 09:37 Out: 10:30 Time: 0:53 Total Time: 6:09
In: 14:30 Out: 15:30 Time: 1:00 Total Time: 7:09
In: 16:54 Out: 17:41 Time: 0:47 Total Time: 7:56
Day 4
In: 07:17 Out: 07:57 Time 0:40 Total Time: 8:36
In: 09:44 Out: 10:33 Time 0:49 Total Time: 9:25
In: 12:04 Out: 12:48 Time 0:44 Total Time: 10:09
In: 14:53 Out: 15:41 Time 0:48 Total Time: 10:57
Day 5
In: 07:24 Out: 07:57 Time: 0:33 Total Time: 11:30
In: 09:12 Out: 10:07 Time: 0:55 Total Time: 12:25
In: 11:35 Out: 12:21 Time: 0:46 Total Time: 13:11
In: 15:00 Out: 15:48 Time: 0:48 Total Time: 13:59
In: 17:01 Out: 17:26 Time: 0:25 Total Time: 14:24 - Note fast current lost buddies and surfaced early.
Day 6
In: 07:33 Out: 08:04 Time: 0:31 Total Time: 14:55
In: 10:06 Out: 10:46 Time: 0:40 Total Time: 15:35
In: 12:14 Out: 12:58 Time: 0:44 Total Time: 16:19
In: 15:13 Out: 15:53 Time: 0:40 Total Time: 16:59
In: 17:00 Out: 17:48 Time: 0:48 Total Time: 17:47
Day 7
In: 07:13 Out: 07:56 Time: 0:43 Total Time: 18:30
In: 09:57 Out: 11:08 Time: 1:11 Total Time: 19:41
In: 11:37 Out: 12:26 Time: 0:49 Total Time: 20:30
In: 15:17 Out: 16:02 Time: 0:45 Total Time: 21:15
Day 8
In: 07:08 Out: 08:19 Time: 1:11 Total Time: 22:26 Note: Last Dive, total dives 29
Computer was showing 18 Hrs 04 Mins no fly time and I boarded the plane back to Dubai with 2 mins no fly time on my computer (Suunto Solution Alpha)
All of the dives were photographic dives and back then it was film not digital, hence some shorter than normal dives for me as I usually surfaced after I ran out of film.
Last edited by Searcaigh; November 24th, 2011 at 05:55 AM.
Reason: Add more information