Drag Down Current in Cozumel or Anywhere?

[AXL72]

I tried searching this site for a post such as the question I am starting (or re-starting), only to come up empty (lots of posts to sort through)

Anyway, have any of you heard of or experienced being dragged to deeper depths by a downward current while diving any of the reefs/walls in Cozumel or anywhere else in the world?

A divemaster used a brief reference to such an incident, which apparantly took an experienced diver from 80 ft to 180 ft, as a harsh reminder to remind everyone on a dive to stick together. He offered very little details or most importantly lessons learned for dealing with this type of situation (shame on him). Is this type of incident an urban legend (or in this case, dive legend)?

Also, what should be done in such a situation?

1. Inflate BC, drop weights?

2. Other details?

3. Other mthods?

Finally, if this post has already been started, can you e-mail the link so that I can quickly find it.

Thanks

 

[Cacia]

I have experienced downdraft currents in Palau on sites like Blue Corner. It does get your attention when you are at 60 ft and then suddenly 90 ft without knowing it happened. Usually this happens near a wall. Someone told me here on Scubaboard to watch the marine life ahead for clues. I thought that was a good tip. Be ready to add air to your BC and watch your gauge in areas with converging currents near a wall. The 80 to 180 sounds pretty extreme but I am sure anything can happen depending on the physics. Usually, I think being aware of where these currents occur and being alert to your depth will be enough to allow you to react The speech about staying together always surprises me. I wouldn't stay with the diver getting sucked to 180ft, unless it was one of my kids. I did not experience anything like that in Cozumel but the current was light when I was there. It could happen anywhere where currents and walls converge. My other opinion is that most split fins put you at a disadvantage in stiff currents.

 

[Rick Inman]

I tried searching this site for a post such as the question I am starting (or re-starting), only to come up empty (lots of posts to sort through)

Anyway, have any of you heard of or experienced being dragged to deeper depths by a downward current while diving any of the reefs/walls in Cozumel or anywhere else in the world?

A divemaster used a brief reference to such an incident, which apparantly took an experienced diver from 80 ft to 180 ft, as a harsh reminder to remind everyone on a dive to stick together. He offered very little details or most importantly lessons learned for dealing with this type of situation (shame on him). Is this type of incident an urban legend (or in this case, dive legend)?

Also, what should be done in such a situation?

1. Inflate BC, drop weights?

2. Other details?

3. Other mthods?

Finally, if this post has already been started, can you e-mail the link so that I can quickly find it.

Thanks

That incident is discussed and referenced in my favorite thread on downcurrents, HERE.

Lot's of reading, so enjoy!

 

[mariebahn]

Not a myth. As one of three survivors of a near-death experience due to a Cozumel downwelling (Palancar wall), I can tell you that it happens. Hit 220' before we were able to reverse direction (with bcs inflated). Don't wish to post details for general consumption, but will share info published in Undercurrents that was available long before our experience (I think the story is from 2000). I also came across an article with statistical information regarding the number of annual deaths attributed to this phenomenon in Cozumel specifically, but will refrain from posting without factual backup.

Cozumel Current Deaths
The Aussies aren’t the only ones who have lost divers of late. Two Colorado women in Cozumel disappeared February 1 from the Punta Tunich dive site. Janie McKibbon, 52, and Regena Hale, 50, both novice divers, were last seen at about 40' when they gave a thumbs-up sign to their Dive Paradise instructor and began to surface. When they didn't appear, he radioed for help, and Mexican navy boats, aircraft, and 50 private vessels mounted a full-scale search but failed to turn up any sign of the women.

Though the reef at Punta Tunich is between 40 and 60 feet, it’s adjacent to a shelf that drops to over 1000. And the undertow there has earned divers’ respect; "If you get caught in that undertow," Dive Paradise’s instructor said, "it’ll drag you right out." The currents that day were described as "off and on and changing." Reader Gary Nagel, who returned from Cozumel just after the accident, reported that on the date the divers disappeared, "winds from the West drove the current to extremes." He also reported the death of another diver from air embolism the previous day.

We wrote about Cozumel currents a few years back after a spate of disappearances. Divers who’d been in their grip described a choppy sea pockmarked by 30-100' areas of placid water surrounded by whitecap rapids. At times a tornado-like funnel swirled in the middle of the calm. Since changes in tide and the mixture of warm and cool water are reportedly responsible, the problem isn’t seasonal.

It is, however, frightening, and staying calm at such a time can be as challenging as the currents themselves. If you get caught in a downwelling or upwelling, however, don’t panic. Instead of struggling against the powerful current, swim out at an angle so you don’t fight its full power. In a powerful undertow, simply inflating your BC may not precipitate an ascent. Instead, drop your weight belt, inflate your BC, and then try to ascend. Should you begin to ascend too rapidly, spread eagle to slow the rate.

Even better, of course, is examining the surface before entry and looking for the telltale signs of raging currents. If you see them, stay out of the water.

 

[Bob3]

Yep, a group of about 6 out of 8 people I know all got bent in Coz from a downwelling.
Got it on video too.
Gotta swim away from the wall.

 

[Doc]

This can occur in may places in the Caribbean, not just at the "holy grail" places like Galapagos.

The key to mitigating is to become instantly aware of the situation. Do this by developing skills that alert you to changes in depth. In order: The feel of the water past your exposed skin, watching your surroundings (reef), watching bubbles (are they going down?), your gauges, others behind you (who haven't entered the downwelling), ear pressure.

The central factor in those swept downward: "I didn't realize it was happening..."

The quicker that you realize... you can swim laterally to get back and away, you can kick like mad towards to surface, you can decide to introduce air into your b.c., you can dump weights, you can take the dozen other steps to correct over ascent now that you're totally hosed up, you can do your best to do a safety stop, you can plan your next day of land based activity because you're off the charts.

Listen to your D.M.

 

[Henryville]

Think of underwater currents like rivers on land. When a current (river) meets some big obstacle like a pinnacle, it will go up and over or around, seeking a path of least resistance. When the river comes to a cliff, you get a waterfall. As the above posters and the linked thread will advise, swimming up the waterfall won't work, but it may be your first instinct. Don't be like a migrating salmon! Swim away from it. The down current is usually fairly localized and most intense close to the wall/pinnacle.

I have experienced a fairly mild version of this in Japan at the tip of the Izu Peninsula (Mikomoto-jima) where a couple of strongish currents come together over a series of rocky pinnacles. You can watch schools of fusiliers "pouring" down the underwater current.

Situaitonal awareness is important. First indicator for me is usually needing to equalize my ears at a moment when I think I am at a constant depth. It is easy to let it get away from you as I have watched inexperienced divers in a group I was with drop 40 feet in less than a minute without taking action or apparently even realizing what was happening.

 

[Ayisha]

On one of my dive group's trips to Coz almost two years ago, this happened to one of our couple's. I was on a different boat than they were, so I didn't see what happened. They told me about it afterward, as did others. They dropped from around 80 feet to at least 130 feet really quickly (I'm not sure of the exact numbers now). Nobody else got caught in this downswelling, only this couple. The instructor on their newbie boat had said that it was probably inexperience and lack of buoyancy control since he had never heard of it, but they insist that they were swept down. After their incident, I started hearing about other ones, so I tend to believe them.

If this thread is because someone is considering going to Coz or anywhere else, don't let those infrequent occurrences dissuade you. The diving is great, and I, as well as most people I know, have never experienced this phenomenon.

In drift diving, like in Coz, we learn to stay close to the wall, wreck, etc., since the current is slower near structures, and that's what I've done. Now I'll have to reconsider how close I go to a wall... :11:

 

[AXL72]

Rick, Catherine, Marie, Bob, Roatan, Ayisha, Henry:

Thanks for sharing your experiences. Rick...thank you especially for the link. I read through those psots intently, just like I have read these latest posts.

I just find this topic the most intriguing and feel there is still much to be learned from it. Surpriing that a topic like this is not mentioned in open water or advanced open water c;asses or trips (maybe I just have not done my research).

I have dove Coz on two separate occasions, and if currents can flow borth/south, I have to agree that they can also flow east / west and down/up. Flying horizontally at 1 to 3 knots over a reef this last time in August in Coz just made me think, what if the current flowed close to the seabed over the wall and downward toawrds depths (scary). This was compounded by the short story by the DM on the boat and wide eyed divers looking at eachother thinking and saying, "what would you do in such a situation?"

I just find this board a must use site and a valuable resource, especially for lessons learned such as this. I think the posts will or have alredy helped to save lives, if not to at least make similar situations less stressfull.

Being a subsea pipeline engineer, I take advantage of the "boundary layer" and seabottom friction to design and install deepwater subsea pipelines without burial and to be exposed to ocean bottom currents. If I had not read these posts about swimming away from the wall, I would have intuitively darted straight to the coral to take advantage of what I would expect to be lower water velocities, if placed in such a siuation. Based on these posts, I would only be unpleasantly surprised, with the possibility of loosing gear, and maybe worse, my prescription (-10) goggles. Ooooh, that would not be good.

I don't know why these downwelling currents act localized in shallow depths (ie less than 200 ft, whereas at deepwater depths around 1000 ft to 5000 ft for pipelines, they act over a greater height above seabed with lower velocities nearer the mudline). Theories or facts have been pointed out or hinted to the following potential reasons with the last one being added as a theory I just want to throw out there (refering to Coz bathymetry) :

1. Perhaps northern or southern currents flow over the flat seabed, sometimes hitting a pinacle or obstrution near a wall, pick speed and concentration to go around it, and maybe with the least resistance being down a wall to greater depths.

2. Perhaps eastern or western currents flow over the flat seabed or open water toward a wall, hit a set of pinacles / obstructions, picking speed and concentration to go around it, cause a pocket of lower pressure around the pinacle(s) / obsticle(s) being pulled / collapsing behind the obstruction(s) and heading dowanward/upward due to lower pressure on the back and low or high sides of the obstruction(s). Wirh the collapsing and draw down/up by lower pressure, the current stream continues with enough momentum to act like an underwater waterfall / upward jet focused / localized to the wall downward or upward. Maybe the least resistance happens to be down a wall to greater depths or if heading in opposite direction towards shore, upward.

3. New potential theory to throw out there: Perhaps a tidal or wave generated current or undertoe like current flows from shore to the wall. once it reaches the wall it meets great resistance by a wall of great height and mass with different water densities and/or temperatures, etc., which force the current downward hugging the wall. This would be analogous to a high pressure system redirecting a hurricane path. Since the current starts off from tidal or wave generation, there is a constant supply of mass, that allows the current to remain strong with little frictional loss to great depths. The current could be turned into more of a monsterous current when obstructed and focussed through channel's/valleys between pinacles / coral heads. Likewise, if the current is flowing from bluewater, it could hit other the wall and shallow water different temperature water mass, which forces the current upward.

Anyway, for what its worth. It might be an interesting discussion to ponder the why's of such observerd observations, also. I hope more continue to post their experiences and stories they have heard to further our knowledge and reaction performance to these occurences.

I know I will be better prepared by all of your responses and history of the topic.



PS...sorry for the novel...and no i do not get paid by the word or character here

 

[ArcticDiver]

Doesn't happen often. But when it does, a downcurrent can definitely accelerate a diver's pulse if it isn't of the garden variety thin stream.

Swimming away from the wall is the first reaction a diver should have. But, sometimes the downcurrent is so thick and so fast that a diver can't swim away fast enough to avoid its' effects. So, staying away from wall diving when strong surface current are running perpendicular, or nearly so, is the best policy.

But, if you do get caught in such a current Prompt and Decisive Action is the only escape. Lots and lots of dispute on what that action should be. L O N G thread on this subject about a year or so ago that aired various people's ideas.