Reef Swim-Through Dangers

[krbailey]

I recently returned from Cozumel where I received my AOW and had a dozen more dives afterwards. On quite a few dives, the DM led us through reef swim-throughs that were quite narrow with several twists and turns. On one particular dive, there was no "light at the end of the tunnel" until we were half way through. I noticed several divers banging into the coral and if you were the last one in line, you were swimming through silt. I am fairly comfortable with my bouyancy skills, but I' far from expert.

I felt this had some of the dangers of cave diving (i.e. limited visibility, opportunities to make a wrong turn, no place to turn around, overhead obstructions etc.)

Is this a common practice?

 

[seaducer]

Yes, it seems to be. DM's love to take people on swim throughs, some of them like you mentioned are long and twisty and tight. There are alot of divers without the skills and experience you should have before diving overheads following the DM's in.

 

[ScubaSarus]

I agree; dive thrus are nice but I need to see the light before entering a dive thru or plenty of back out clearence with a buddy behind me (not going in yet) incase of a snag.

 

[Bubbletrubble]

Yup. This happened when I was there a couple of years ago. I found that some divers would get hung up on the ceilings of the swim-throughs due to poor buoyancy control. One unfortunate guy had a nice gash on the top of his forehead from scraping his head on one of the swim-throughs.

I was comfortable going through the holes, so I did most of them. I opted out of a couple because I would have been at the end of the conga-line...with silted out conditions. I just hung out at the entrance for a few seconds to witness the pile up...and then swam around to see where the group exited. No big deal. There really wasn't anything to see inside anyway.

As I recall, the DM told us beforehand that the swimthroughs were entirely optional. Despite this, I suspect that some people were just following the DM blindly.

For the swimthroughs that I did, I would say that the biggest concern would be that a diver would totally freak out inside, become too positively buoyant, and get plastered to the ceiling. The DM would notice that his conga-line got hung up somewhere...and would have to rescue the diver lodged in the swimthrough. In that case, the conga-line behind the diver might have to back out unceremoniously. What a mess that would be!

I totally agree with you that those swim-throughs could be dangerous...although I don't recall ever hearing about a Cozumel dive incident involving one of them.

 

[Garrobo]

Uh-huh. I learned the hard way about cutting my bald head and hands when diving wrecks. From then on it was gloves and a beanie.

 

[deco_martini]

Swim throughs on cozumel are pretty weak sauce. Even with the silting they aren't very bad. You still have lots of light and the squeeze isn't really that tight. Going through them is very common.

Now, there is a dive called "The Devil's Throat" where the swim through does get tight and you get complete darkness. You come out of that swim through at about 120 feet. The better DMs on coz won't take divers there if they notice their skills are poor.

 

[jva]

I went on a boat dive with a DM a couple of weeks ago. I thought it was well planned and we agreed on a maximum depth of 40m. When we didn't encounter any sharks, the DM decided to go down to 55m where he took a long swim-through (narcosis?) and I was perplexed to see the rest apparently blindly following him...

My buddy and I did not, and while the rest was swimming through the underpass, getting a deco obligation, we were the only ones to see an oceanic white tip (twice actually, or two of them).

That was a lesson in how blindly some people are willing to follow a DM for me!

Edit: OT, but do you think this was due to nitrogen narcosis? Also the DMs decision?

 

[don Francisco]

There is a gray area between swim throughs and caverns. My two guidelines in telling the difference are the ability to see the exit opposite before entering and/or the infallible path to an exit such as in a short tunnel with no branches.

Cozumel DM's often take less than ideally qualified divers through longish swim throughs, but all of them fit either of the above definitions. Is it best practice? Probably not, but is it dangerous? Again, not really. Given the many, many, thousands of divers that have gone through these swim throughs over the years, the safety record speaks for itself.

Most DMs in Coz will brief an alternative to doing the swim throughs for those uncomfortable with tight situations, either around, or over following the bubbles. The better ones gauge the their charges skills before doing the tighter swim throughs, such as Devils Throat. I personally avoid the swim throughs since they are generally sterile & I prefer to use the opportunity to look for photo subjects nearby.

The only serious danger of this practice is that it might mislead a diver into believing that it's OK to enter a passage that isn't as thouroughly vetted as the Cozumel swim throughs.

In summary, Ideal? no. safe? yes.

 

[TASims]

I guess its common enough. I like going through them too, but I don't like the silt. I bet most tourist/divers feels like they are doing soome "high Adventure" dive or are participating in a Deep Sea Detectve episode or something.

 

[fdog]

Probabally not a popular thought here, but...<shrugs> overhead-restricted is....overhead-restricted.

Just ask yourself "what if". If you had a gas failure inside a nice long swimthrough, could you count on your buddy (and yourself) to know what to do, and then, do it?

If you can't immediately answer that question with a yes, then that swimthrough is a bad place to be.

Casual overhead-restricted kills just as easily as the serious stuff. Yes, lots of folks have done it - doesn't make it the right thing to do - you're possibly betting your life on the flawless performance of your regulator.


All the best, James