Trip Report Why I Won't Be Returning to Cozumel-Part 1,2&3

[yle]

The older I get, the more conservative (diving-wise) I become. A Cozumel dive I used to enjoy a lot is Punta Sur Cathedral, but the way I have always been taken on that dive I incurred a deco obligation at the end, and my last dive there I got what I found out later was likely a minor skin bend. I don't do deco any more.

Yup. I point out to my OW students that everything on the list of DCS risk factors is within our control... except age. Enjoy it while we can.

 

[boulderjohn]

But everyone is different. You might do just fine with four dives a day, multiple days in a row, but the data collected from the diving public at large, over many years, suggests that this kind of schedule is on the riskier side of that statistical curve that determines the probability of a DCS incident.

If it works for you, then keep at it and dive as much as possible. But consider that you could possibly be exceptional (in terms of DCS risk tolerance), and we wouldn't want the average diver to assume they are also.

The evidence is by no means thoroughly established, but there are indications that after diving multiple days, you are less prone to DCS, not more. A talk given by a DAN representative at my dive shop years ago gave statistics that I can't recall precisely, but the incidence of DCS is significantly greater on the first day of a dive trip (and the first dive of a trip) than on subsequent days and dives, Yes, it is true that the facts that you don't dive after you get DCS and some people only dive a few days means that DCS on the first day is statistically more likely than later days, but the numbers went well beyond that probability.

 

[yle]

The evidence is by no means thoroughly established, but there are indications that after diving multiple days, you are less prone to DCS, not more.

So... four dives a day for multiple consecutive days might present a greater risk for DCS, or it might present a lesser risk of DCS. Which means it could present an equal risk also.

Interesting. It's almost like this suggests that there is a strong random element to DCS probability which would require conservative diving practices to reduce the risk to an acceptable level.

 

[MrBigfins]

The evidence is by no means thoroughly established, but there are indications that after diving multiple days, you are less prone to DCS, not more. A talk given by a DAN representative at my dive shop years ago gave statistics that I can't recall precisely, but the incidence of DCS is significantly greater on the first day of a dive trip (and the first dive of a trip) than on subsequent days and dives, Yes, it is true that the facts that you don't dive after you get DCS and some people only dive a few days means that DCS on the first day is statistically more likely than later days, but the numbers went well beyond that probability.

My understanding of the risk being higher on first day is due to fatigue from travel day, likely dehydrated from travel day and the general stress from the travel day. Don't take any of that as fact, but I do remember reading several articles and discussions on why that was the case.

Your profiles, habits, age, and factors we don't even know to consider play a part in the risk for each person. There is a reason it's called decompression THEORY.

However there are 10s of thousands of divers who do 4-5 dives a day on liveaboard trips each year, all around the world. The thought process that 4-5 dives a day is in and of itself on the high risk spectrum doesn't seem well supported. If you are pushing ndl on all those dives, or squeezing surface intervals, or not diving best mix for your profiles then I could agree. It's all about balance in my opinion.
Balance of acceptable risks, mitigating what risks you can to lessen adverse outcomes and making educated decisions

 

[MrBigfins]

The older I get, the more conservative (diving-wise) I become. A Cozumel dive I used to enjoy a lot is Punta Sur Cathedral, but the way I have always been taken on that dive I incurred a deco obligation at the end, and my last dive there I got what I found out later was likely a minor skin bend. I don't do deco any more.

I love Cathedral, one of if not my favorite dive in Coz. I've done that dive with several different ops and plans and it can easily be done without deco obligations. The decision on how to mitigate your risks are something every diver should be conscious of.

 

[ReefHound]

My understanding of the risk being higher on first day is due to fatigue from travel day, likely dehydrated from travel day and the general stress from the travel day. Don't take any of that as fact, but I do remember reading several articles and discussions on why that was the case.

That's what I remember hearing about it, too. Plus there is a tendency for "first night" party and cutting loose.

 

[scubadada]

We now have more modern tools to help us limit our risk, like SurfGF. I have been diving since 1970 with Navy tables, a watch, and a capillary pressure gauge. I did not have a SPG until 1972. I used to do a longer SS or pad my light deco to limit my risk. Now, there is little guesswork, I simply follow my SurfGF to limit my DCS risk.

 

[Damselfish]

However there are 10s of thousands of divers who do 4-5 dives a day on liveaboard trips each year, all around the world. The thought process that 4-5 dives a day is in and of itself on the high risk spectrum doesn't seem well supported. If you are pushing ndl on all those dives, or squeezing surface intervals, or not diving best mix for your profiles then I could agree. It's all about balance in my opinion.
Balance of acceptable risks, mitigating what risks you can to lessen adverse outcomes and making educated decisions

One thing that is different on liveaboards is that surface intervals tend to be longer. On a 2 tank dayboat you will typically get an hour max but often less. Also on the LOB you may expend little effort on anything after dives beyond strolling to a lounge chair for a snack and a nap.

 

[ggunn]

I love Cathedral, one of if not my favorite dive in Coz. I've done that dive with several different ops and plans and it can easily be done without deco obligations.

I do not doubt that it is possible to dive the Cathedral without going into deco, however, in the many times I have gone to that site with at least four different dive ops, the path taken through the site has invariably been through several swimthroughs with the last one being the big one that gives the site its name, and coming out of it deep with a deco obligation. When I was younger that sort of thing did not bother me, but these days I do not do deco diving any more, and I don't dive as deep as I used to.

 

[rmssetc]

The evidence is by no means thoroughly established, but there are indications that after diving multiple days, you are less prone to DCS, not more.

I wonder how much of that is because people who do multiple dives/multiple days are a self-selecting population, and they are more aware of DCS risks/precautions than someone who only intends to do fewer & less frequent dives.

The "bent on the first dive" diver may not be aware of their computer settings, not be familiar with the NDL display, may be in less fit physical condition, etc.

It's also possible that the less frequent diver is trying to maximize the experience, and rationalizes a riskier profile (closer to the NDL limit, more rapid ascent) because they don't plan to dive repeatedly and believe that puts them at a lower chance of DCS.