Tourist lost - Cozumel

[Snoweman]

I used to do this. Then after reading various posts on here I decided that, for me, if you look at a PPO2 of 1.6, then the likelihood of exceeding the MOD when diving 32% EANx was fairly small -- if we ended up diving Devil's Throat that might happen by 2 feet for a very small amount of time before I would start ascending.

Weighing that against the nitrogen loading/possible deco (with perhaps not much air left for deco stops diving single tank) I decided that for me just diving all 32% tanks may be the way to go. I'm not advocating anyone else do this, and I don't recall all that I read that lead me to this (definitely included discussions of 1.4 versus 1.6 PPO2, and also the amount of time at depth as a factor), but for me that's been somewhat simpler than different mixture tanks. Plus those dives to the 1.6 MOD limit are very rare (at least with dive ops I usually use). YMMV

My worry is either a sudden down welling or having to chase a diver down that is not paying attention to their depth.

 

[Rob9876]

My worry is either a sudden down welling or having to chase a diver down that is not paying attention to their depth.

I think each diver has to assess the probabilities and weigh them -- your concern is within the realm of possibility. As for me, most/all of my >100 foot deep dives in Cozumel are not wall dives (where down currents are of most concern). But crazy down currents could be anywhere I guess.

And I'm not a DM/Instructor, so though I try to be a good insta-buddy honestly I'm not likely to chase an insta-buddy very far at all past the 32% MOD at 1.6. I would chase my son to the abyss if I had to, but we've been diving together fairly often for years now and he's a very capable & responsible diver (and I've told him not to endanger himself to help me).

So, individual factors can vary and I'm not telling others what to do. But this is what I've decided to do based on my experience so far, sites my dive op usually dives deep on, and my likely buddy scenarios.

 

[Nemrod]

I guess we have been back from Cozumel two weeks now. The current was ripping and going every which away, including down. Heading back again in a few weeks. I think 32% for Devils Throat is okay (for me). Used air this past trip but really I was only at 121 feet and only for a couple of minutes if that long. On air I went into deco, everyone did, which cleared as we worked out way down the reef. I had, if I recall, about 800 to 900 psi on deck remaining.



It really is not one of my favorite Cozumel dives but everyone always wants to do the Throat so I go along. Here is the one in particular where there was a down current encountered at the end of the dive that swept us downward strongly just as we were getting to our safety stop:

 

[Johnoly]

was a down current encountered at the end of the dive

That graph will get your attention quick...
2 questions about that dive (I'm just curious)
a) What mix was that on?
b) How many dives did you do the day before and were any 'close' to deco ?

A big problem with dive friends has been the day prior spent deco diving, then diving the next morning. Their 1st dive starts and ends with the computer in the green. But micro bubble hits are happening when the diver on his SS see's a fish on the bottom and 'bounces' back down to get it. Even if doing a full resume of the 3 min SS, we're still seeing divers get a hit from that bounce, all while the computer is NDL green.

I've stopped doing 'bounce-backs' because of it, not even shallow ones.

 

[ChuckP]

I guess we have been back from Cozumel two weeks now. The current was ripping and going every which away, including down. Heading back again in a few weeks. I think 32% for Devils Throat is okay (for me). Used air this past trip but really I was only at 121 feet and only for a couple of minutes if that long. On air I went into deco, everyone did, which cleared as we worked out way down the reef. I had, if I recall, about 800 to 900 psi on deck remaining.



It really is not one of my favorite Cozumel dives but everyone always wants to do the Throat so I go along. Here is the one in particular where there was a down current encountered at the end of the dive that swept us downward strongly just as we were getting to our safety stop:

30 minute dive at Devils Throat? Ugggghhh, give me my money back!!!

Where was that second dive at? Looks like you might have hit a little eddy/whirlpool if you were in shallow water - little air in your BCD, doesn't take much to drop you 30 feet

 

[Nemrod]

That graph will get your attention quick...
2 questions about that dive (I'm just curious)
a) What mix was that on?
b) How many dives did you do the day before and were any 'close' to deco ?

A big problem with dive friends has been the day prior spent deco diving, then diving the next morning. Their 1st dive starts and ends with the computer in the green. But micro bubble hits are happening when the diver on his SS see's a fish on the bottom and 'bounces' back down to get it. Even if doing a full resume of the 3 min SS, we're still seeing divers get a hit from that bounce, all while the computer is NDL green.

I've stopped doing 'bounce-backs' because of it, not even shallow ones.

Cozumel it is typical to do two boat dives a day and then either a night dive (boat) or an afternoon dive (boat or behind resort). That was near the end of a long trip. As to a bounce, that was a down current. You will notice that we did a fairly long safety stop and a gradual ascent after recovering from the down current, it was a STRONG current! Excrement happens . The mix was alleged to be 32% but since the dive resort did not have a functional instrument --- I am not sure. At my insistence they got a meter and demonstrated the 32%. Okay, I guess, it is what it is. This resort used a fill service, they were not doing their own filling. I rarely climb back aboard with less than 700 psi unless it is intentional (to test something at low pressures etc.). The red line in the first graph is a deco obligation (that cleared), the second graph has no deco obligation at any point..

 

[Nemrod]

30 minute dive at Devils Throat? Ugggghhh, give me my money back!!!

Where was that second dive at? Looks like you might have hit a little eddy/whirlpool if you were in shallow water - little air in your BCD, doesn't take much to drop you 30 feet

Not sure I follow? The dive at the Throat was 43 minutes and continued on along the reef line. I get bored real quick with the Throat and prefer to get along back on top where there is something to see potentially. The dive terminated when everyone but me was at 700 psi and needed to do the safety stop. I was back on deck with at least 800 psi. Let me clarify, my limits for a dive are rarely dictated by my limitations but by the other divers running low on air, or, the desire to avoid getting bent, at 70 yo I try to be a little conservative now and then .

Yes, the blip at the end of the second graph is a down current. I thought I said that? I posted that graph because of the discussion about down currents along the wall in some Cozumel locations, depending upon current directions, it can happen and they can be strong. That graph shows a down current.

The two graphs are not consecutive dives, note the dates. I think the second graph is Tormentos or that area.

 

[ChuckP]

Not sure I follow? The dive at the Throat was 43 minutes and continued on along the reef line.

I don't really count the time spent at 30' as the "dive", yes you are diving but....... There is nothing at 30' unless you swam 5 minutes to the shallows over sand.

There are much better profiles to do there that give you much more time on that formation or if the currents are working with you, take you to shallow area is what I am saying.

You are Sam aren't you? If it is you, why are you diving like that lol

 

[Nemrod]

I don't really count the time spent at 30' as the "dive", yes you are diving but....... There is nothing at 30' unless you swam 5 minutes to the shallows over sand.

There are much better profiles to do there that give you much more time on that formation or if the currents are working with you, take you to shallow area is what I am saying.

You mean the sand where the eagle rays cruised by?

I will be there in November, again, and hopefully will not be drug back through the Throat, I will just say it, it might be my least favorite Cozumel dive. Enough of this, moving on along now. Getting way off topic.

 

[scubadada]

30 minute dive at Devils Throat? Ugggghhh, give me my money back!!!

I don't really count the time spent at 30' as the "dive", yes you are diving but....... There is nothing at 30' unless you swam 5 minutes to the shallows over sand.

There are much better profiles to do there that give you much more time on that formation or if the currents are working with you, take you to shallow area is what I am saying.

Agree. My son and I last did Devil's Throat with Aldora on air, HP 100s. Max depth 127 feet, dive time 65 min. We had a very short deco obligation that cleared before the safety stop. Not the best dive off Cozumel, but this one was good.