NITROX for any and all dives?

[bladder]

First dive of the day is always the deeper dive in Cozumel and we would do that on air, then switch to ean32 for the 2nd and 3rd dives.

I cannot wrap my head around this one.

 

[woodcarver]

A lot of the first dives would be on a wall with no bottom. This was the logic as explained by my instructor at the time who suggested doing it this way.

 

[bladder]

A lot of the first dives would be on a wall with no bottom. This was the logic as explained by my instructor at the time who suggested doing it this way.

There's not much to see deeper than 100' on most dives in Cozumel and I'm going to wager a guess that you never even exceeded this depth regardless of how far above the ocean bottom you actually were.

The benefits of Nitrox are greatest between 60-100' which is probably where most of your diving was done during your first, deeper dives, as compared to the second and third shallower dives which were probably between 30-50', is that about right?

If so your instructor gave you some really BAD advice.

 

[woodcarver]

Actually went below 100' several times on those dives, but never would have exceeded the mod for the 32%. And you are correct, there's not much to see. Although I would like to dive Santa Rosa and Palancar in the afternoon sometime. Since they are always the first dive in the morning, the walls there are always in the shadows. I think with the afternoon sun hitting them, there would be a lot more to see.
The others, 2nd and 3rd dives, rarely were deeper than 70-80' and usually in the 40-60' range. At that time in our diving, we (me) were running out of capacity not ndl. But the nitrox did seem to help her. 1st trip, we only did a couple afternoon dives because of the headaches. 2nd trip, we did a third dive almost every day.
I think he was (rightfully) concerned with her bouyancy

 

[bladder]

Actually went below 100' several times on those dives, but never would have exceeded the mod for the 32%.

As I suggested, Nitrox would have been a significant benefit on those deeper first dives. Even though you exceeded 100' you surely didn't spend much time there. It's not like there was a wreck down there or something worth burning through your tank in under 10 minutes.

The others, 2nd and 3rd dives, rarely were deeper than 70-80' and usually in the 40-60' range.

As I said, there is no significant benefit to Nitrox at 40-60' depth which is where most of your subsequent dives were done, using Nitrox at the questionable advice of the very questionable instructor.

At that time in our diving, we (me) were running out of capacity not ndl.

The Nitrox is still a benefit on the dives in the 60-100' as far as less N02 absorption especially over multiple dive days even if you ran out of gas before hitting your NDLs.

I think he was (rightfully) concerned with her bouyancy

If your instructor was concerned with her buoyancy, it baffles the mind as to why he'd put her over an essentially bottomless wall.

 

[tursiops]

If your instructor was concerned with her buoyancy, it baffles the mind as to why he'd put her over an essentially bottomless wall.

I'm guessing you are not an instructor? There is a difference between someone having buoyancy problems versus someone having problems AND potential oxygen toxicity problems. Risk mitigation.

@woodcarver Actually, the headache sounds like possible CO2 buildup, not DCS.

 

[woodcarver]

Yes, fully understand that now. At the time, not so well. Learnt much in the last few years. There's actually several things we would do differently if we could go back and repeat those trips with current knowledge as opposed to the freshly minted card carriers we were at the time. That return trip is in the planning stages at the moment.
The DM led us, our instructor was not with us on that trip.

 

[bladder]

I'm guessing you are not an instructor? There is a difference between someone having buoyancy problems versus someone having problems AND potential oxygen toxicity problems. Risk mitigation.

Thanks, had to think about what you wrote but I get it now. And no, not an instructor, just a regular diver here.

 

[woodcarver]

Thanks tursiops, that would make more sense. She is not as comfortable in the water but is absolutely fascinated with what she's seeing, so I dive to her comfort level. She's come a long way in 4 years.

 

[tursiops]

Thanks, had to think about what you wrote but I get it now. And no, not an instructor, just a regular diver here.

You are absolutely correct about the optimal nitrogen management being Nitrox on the first dive, and perhaps not on the later one. But there is more to the equation that just nitrogen management....in this case, oxygen management!