Multi-day repetitive recreational profiles?

[Gombessa]

Testing the waters of the practitioner's forum:

I've got a weekend liveaboard trip coming up soon, with the potential for up to 15 dives over 3 days. We're doing only recreational profiles, on 32%, and I think it's safe to assume that a lot of these dives will allow for more aggressive MDL profiles if we want (e.g., closer to 100fsw for 30 minutes rather than 40fsw for 60min). These dive-all-day trips aren't my usual baliwick and I don't recall discussing residual loading for repetitive dives on multiple days with my instructors. So while that's pending, I was hoping you fine folks could share your thoughts/experiences on how you handle or don't care to handle for these types of trips. Thanks!

 

[RTodd]

You will find that 5 dives a day for multiple days is just too much to be enjoyable. 4 nice 1+ hour dives is all you can comfortably get in on a liveaboard. Maybe a night dive on one of the days. Actual deco profiles are less important than staying completely hydrated and ticking all of the other boxes. The issue is that, if you really do 5 a day, you need to dial it back a bit on the conservatism scale because odds are you will screw up something a little and this can get compounded doing this many dives. Yes, you should be clean overnight but you need to make sure you don't create any issues during the diving day.

Other than that, my usual advice is to run some fairly aggressive multi dive scenarios on deco planner and you will be suprised with how much even the models will let you do.

 

[Peter Guy]

Gombessa -- this is exactly why I'll have an X1 on my wrist! And I don't think I'll be doing more than 3 dives a day due to my old man status! (Hmmm, I just had an awful thought -- I think I'll be the oldest person on the boat!)

 

[TSandM]

Peter, I am quite sure an X1 is NOT a solution for the DIR Practitioner's forum . . .

It is a reasonable question, though. I think the procedures we use for determining our decompression status work well, in part because there is SO much conservativism built into the models on which they are based. But if they were ever to fail, it would be in the face of repetitive long, deeper dives over a number of days. My guess is that the n of DIR divers doing recreational liveaboards and multiple dives over multiple days is too small to be able to say for sure that the "double the shallow stops" approach "works", even if it passes DecoPlanner muster.

However, it has worked for ME on a two to three dive a day trip to Cozumel, so I'm content to continue to use it for the CI trip. I find cold water diving too tiring to do four a day, anyway

 

[lamont]

2-3-5 deco or something like that would clean up quite a bit and keep you clean going into the next dive.

 

[lamont]

I know its gauche to followup to yourself...

But one of the things that I've noticed with people on scubaboard who post that they were bent after recreational dives is that usually they've got 2 or 3 back-to-back recreational dives with bad deco or bounce dives on all of them. I don't think I've ever seen someone who has stuck to the single-dive NDLs, even with aggressive SIs that violate residual diving NDLs, who didn't bounce and did a useful amount of deco post about getting bent.

 

[RTodd]

2-3-5 deco or something like that would clean up quite a bit and keep you clean going into the next dive.

This is definately the conservative approach. For recreational diving, what I think works much better and keeps the dive fun as opposed to a mini deco dive is to just do them all as ML dives, 20-40 min at 100-90, slowly moving to 70-60 depending on the site, 5-30 or so minutes at that depth depending on the first portion, then a slow move up to 40-30. Then a reasonable but not very long true deco out from 30. You can repeat this sequence 5 times a day if you really want to.

 

[lamont]

This is definately the conservative approach. For recreational diving, what I think works much better and keeps the dive fun as opposed to a mini deco dive is to just do them all as ML dives, 20-40 min at 100-90, slowly moving to 70-60 depending on the site, 5-30 or so minutes at that depth depending on the first portion, then a slow move up to 40-30. Then a reasonable but not very long true deco out from 30. You can repeat this sequence 5 times a day if you really want to.

Yeah, I was thinking square profiles off a boat with a deeper bottom. If you can multi-level it then it should be easy... just spend some time at 30 or above looking at the stuff there...

 

[Gombessa]

Thanks all! I don't know what kind of opportunities we will have for multilevel dives, but spending a few more minutes on the shallow stops sounds like a good plan. I'm not expecting to last 5 dives a day, but the opportunity may be there and I want to be prepared in case I'm feeling particularly energetic.

 

[amascuba]

I've done a couple liveaboards. Most of the dives were between 60 - 100 fsw with an average run time of 60 minutes. It's definitely important to clean up at the end of the dives. Lamonts 2-3-5 will clean up quiet nice. Also hydrate between dives and enjoy yourself. If you need skip a dive, then skip one. Have fun!