current

[Dave616]

After years of reading (and occasionally feeling anxious) about down currents in Cozumel, I got to experience a real live Cozumel down current today. Here's what happened...

Thank you. I sent this link to my wife to read. Neither of us have been in a downwelling.

 

[PeterNBiddle]

We've never experienced one, and won't complain if we never do, but downwellings are like lightning --- I think you should know what to do or not do even if the odds are remote. We've all been taught since elementary school that you don't go out to the middle of a golf course or climb a tree during a lightning storm.

So, I've had it in my mind, that the first or preferred course of action would be to stabilize depth while swimming parallel to the wall and then ascend when the downwelling subsided enough to allow that. The second plan would be to swim away from the wall.

It sounds like from reading your account, that my option number one would have been an unmitigated failure.

Please comment.

It's a 50|50 split for unmitigated failure! (YMMV! Anyone with experience in multiples of these, please speak up!)

What goes down must come up - if you are in a down current then sooner or later there will be an up current. In between there may well be a cross current, because all currents are circular.

There's one problem with your set up - you are assuming you will know where the wall is. I knew, but at least 2 people on the dive didn't. So let's make this a worst case scenario and say you had no idea where the wall was.

If you headed East, towards the wall, you basically would have dived my dive.

If you headed North (roughly parallel to the wall) I think you might have gone deeper than I'd care to because stabilizing in the blue water would have been challenging but you would eventually have come to an up part of the current, which I know was North of our drop. You'd then be trading one set of problems for another, because you'd be dumping air, inverted and kicking to try to keep from rocketing to the surface.

This was (roughly) Cindy's dive - she knew where the reef was but she was helping another diver. So I think you'd have been okay.

If you headed west - away from the wall - I think you might have wound up similar to Cindy's dive, only much further out in the channel. I hypothesize this because that's more like where the DM wound up with her group. I hypothesize that down currents need large un-yielding surfaces to respond to - like walls. Sooner or later they will dissipate, given enough water to swallow them up.

If you headed South, which is parallel to the wall and so would have been one of your two planned options if you did know where the wall was? I think that might have been a Very Bad Option Indeed.

South would have you fighting the northerly current - the one we dive in all the time - plus a down current. You may have burned a couple thousand PSI going nowhere but down.

Eventually you would tire of that and go somewhere else, because you are not an idiot, so the question is how much tragedy debt would you have accrued in the meantime? Based on what we saw you could have hit 200 feet (or a lot more? Or less? Who knows?) of depth on EAN 36. Not a fantastic option.

Sorting it thru, here's my takeaway:

Plan A: If I know where the wall is, I'm heading for it no matter what. If i clearly can't make progress at all then I will go to Plan B.

Plan B: if I truly don't know where the wall is or the wall is entirely inaccessible I will concentrate on reversing my descent and kick with the current (cross preferably if available, perpendicular to the down if not) and I'll use daylight for up. In other words, I'll do plan A towards a wall that might not exist, because intention.

Treat daylight as your wall and find the best path to it.

(Edited to clarify kicking with the current.)

 

[ggunn]

What goes down must come up - if you are in a down current then sooner or later there will be an up current. In between there may well be a cross current, because all currents are circular.

I don't think this is necessarily true. The only time I have encountered a current like this was at Barracuda. The current was running at about a 45 degree angle to the wall, fast over the top of the wall and down the blue water side. The wall was sloping upward as we were carried that way by the current, so the farther we went the worse it got. I don't think there was a corresponding upwelling.

Plan A: If I know where the wall is, I'm heading for it no matter what. If i clearly can't make progress at all then I will go to Plan B. .

In the case I encountered that would have been a mistake because all along the top of the wall was where the problem was. We swam out from the wall a ways out of the "waterfall", and when we got past the part of the wall that was sloping upward and at that angle to the current, things calmed down and we could get back to it and continue the dive. It wasn't as extreme a situation as the one you got caught in, of course.

 

[PeterNBiddle]

I don't think this is necessarily true. The only time I have encountered a current like this was at Barracuda. The current was running at about a 45 degree angle to the wall, fast over the top of the wall and down the blue water side. The wall was sloping upward as we were carried that way by the current, so the farther we went the worse it got. I don't think there was a corresponding upwelling.



In the case I encountered that would have been a mistake because all along the top of the wall was where the problem was. We swam out from the wall a ways out of the "waterfall", and when we got past the part of the wall that was sloping upward and at that angle to the current, things calmed down and we could get back to it and continue the dive. It wasn't as extreme a situation as the one you got caught in, of course.

I don't think your experience contradicts mine wrt how currents behave - they simply have to be circular or there would be gaping holes in the water. Your current might have shifted 1 yard from you or 1 mile from you, but sooner or later something has to fill in the hole.

We had down current the entire time. It was more manageable at the top of the wall in that we were able to hold coral and not get ripped free. It just wasn't as strong as it was elsewhere.

That said - if my Plan A wasn't working then Plan B would have been exactly what you did. That's why there's a Plan B.

 

[Bubbles below]

Wow, I'm glad everyone is safe! I did my SSI Advanced in Bali last year and one of my specialty was currents, drifts, and waves. I encountered 2 longshore down current during my course. I went to an easy 20ft and quickly to 109ft in seconds! And a ripping current after I completed the class for a fun dive. My long shore down current, I had to swim perpendicular to get out of it. On the ripping current, we were close to wall and held on to anything that didn't move until it pass. I didn't know that Cozumel have that kind of currents like Bali. We are going to be there next week. I hope it subside. Now, I'm worried because my husband doesn't have his Advanced, eventhough, he has 40dives since we started in Sep 2013. This is our first time in Cozumel.

 

[cvchief]

Ibut sooner or later something has to fill in the hole.

.

Gun, translating for you:

[youtubehq]kK62tfoCmuQ[/youtubehq]

Since we are talking about 'troubles.'

 

[ggunn]

I don't think your experience contradicts mine wrt how currents behave - they simply have to be circular or there would be gaping holes in the water. Your current might have shifted 1 yard from you or 1 mile from you, but sooner or later something has to fill in the hole.

In the case I witnessed the "hole" was filled with the reef. The current was restricted between the surface above and the reef below, and when it cleared the reef it spread out vertically (downward). Looking at it another way, the "up" happened first when the current hit the reef. Of course, in the grand scheme of things it was circular - it was part of the Gulf Stream, after all - but that's a pretty big circle.

 

[gfaith]

A little older link here discussing down currents.

http://www.scubaboard.com/forums/ba...7338-diver-down-current-best-action-take.html

Dan Volker has a cool video where he is filming a Triton sub descending and he get caught in it's down draft.

MMM has some good observations as well.

 

[JFS]

There is only 1 area that you may experience a downwelling at Cantarall. I have done this dive hundreds of times and know the area extremely well. The area in front of Los Brisas is where this occurs. Sometimes the surface is calm sometimes its bubbling, either way it can be deceptive. The ONLY way you can be sure of problems is if your Divemaster jumps in at this area and checks. If they do not, then they are not doing their job. Even if the current is funny, the dive can be completed with proper briefing.

 

[PeterNBiddle]

There is only 1 area that you may experience a downwelling at Cantarall. I have done this dive hundreds of times and know the area extremely well. The area in front of Los Brisas is where this occurs. Sometimes the surface is calm sometimes its bubbling, either way it can be deceptive. The ONLY way you can be sure of problems is if your Divemaster jumps in at this area and checks. If they do not, then they are not doing their job. Even if the current is funny, the dive can be completed with proper briefing.

Our DM checked thoroughly, of course. As we all found, the down current didn't happen until 20-30 feet under. Surface seemed normal.