Timing of Dives

[Pulmcc]

We will be going to Cozumel in a few weeks and will be able to dive 4 days. We have to complete our SSI Deep Diving Specialty Diving certification so will need to do 4 deep dives. If we do two of those dives each day on consecutive days but also want to do 2 fun dives each day (so total 8 dives over 2 days), does it matter which dives we do in the morning vs afternoon? I vaguely recall reading that if you want to do 4 dives in a day, you do the deep dives in the morning and then the shallower dives in the afternoon. Is that correct? Also, would diving with Nitrox on the non-deep dives be a good idea?

 

[rick00001967]

perhaps consider doing a 2 dive morning trip each of the 4 days (deep first dive / shallower second dive). then add in a really shallow shore dive in the afternoons?

i personally would not be doing 4 dives in a day.

nitrox never hurts as long as you are within your max depth. you can also dive nitrox but plan your dive time as if you were on air for extra conservatism.

my wife and i did this whenever i was on nitrox as she was never nitrox certified and was on air.

 

[DiveLikeAMuppet]

The order of the dives doesn't matter but if you are using certain computer brands and algorithms (Suunto and RGBM), you might get a very low no-stop time on the subsequent dives if they are deeper, as these computers tend to punish you for reverse profiles.

Your deep dive course should include a bit of theory that would explain why it would be safer to limit yourself to 2-3 dives per day at these depths with sufficient surface interval.

Nitrox is always a good idea, especially with many repeated dives, just pick the right mix for the right dive site.

 

[grantmac]

Keeping your deep dives well away from NDL would likely be a good planning component.

Also for me I find longer dives more fatiguing so two deep dives, so long as they aren't high effort, might be similar to 1 longer shallow dive. This of course also depends on the effort required to get in and out of the water.

 

[dmaziuk]

Original DSAT report recommended "taking every 3rd day easy" with that sort of load, but their schedules were taking every dive right up to NDL, and I think shorter than 1 hour surface intervals... nitrox on shallow dives will reduce your inert gas loading and give you an extra safety margin.

I would think the main problem with 4 dives/day from shore would be that with roughly 1 hour dive time and 1 hour SI this will add up to 7 hours at a minimum and the whole thing will feel like work rather than "recreation".

 

[arkstorm]

I vaguely recall reading that if you want to do 4 dives in a day, you do the deep dives in the morning and then the shallower dives in the afternoon. Is that correct?

That used to be the conventional wisdom but it turns out there is no actual data to support it.

 

[Dan G]

If you are diving with the same op for all of your dives, including the course, I would expect that your instructor or the shop will keep in mind which sites to go to for your dives. In Cozumel there is quite a variety of depths available.

For the SSI deep specialty, not every dive is super deep. A Google search returned these results of the depth range for each dive in the SSI Deep Diver Specialty.

• Dive 1: 18 to 30 meters

• Dive 2: 24 to 30 meters

• Dive 3: 30 to 40 meters

I Cozumel, the Nx options are 32% and 36%, so Nx is definitely a good idea for most of these. For your deepest dives, you will need to dive air.

 

[inquis]

That used to be the conventional wisdom but it turns out there is no actual data to support it.

Yes and no. It's a fact that diving deep first allows more total bottom time for a given SI and depths. This was historically misconstrued into a DCS issue, which is what has zero data to support (as you mentioned).

 

[scubadada]

Original DSAT report recommended "taking every 3rd day easy" with that sort of load, but their schedules were taking every dive right up to NDL, and I think shorter than 1 hour surface intervals... nitrox on shallow dives will reduce your inert gas loading and give you an extra safety margin.

I would think the main problem with 4 dives/day from shore would be that with roughly 1 hour dive time and 1 hour SI this will add up to 7 hours at a minimum and the whole thing will feel like work rather than "recreation".

I've been diving DSAT since 2002, 2300 dives. I have never taken a dive day off during any series of dives. I have often done 4 dives per day, 5 only a few times. These dives were not up against the NDL. So far so good. I have had a Shearwater since 2019, do not surface with a GF greater than 80.

 

[CT-Rich]

Four dives in a day is quite a bit of diving and you will want a decent surface interval between the two deep dives. Three dive in a day and an option on night dive would be what I would do. Nitrox will be good for the shallow dives. If you are in good shape I think it will be fine, but if you aren't, I would avoid making it too demanding.