First-hand account of down current, with video footage

[DandyDon]

There is often a lot of discussion on currents. Hardly ever a mention of tides which tend to peak a couple of days after a new and full moon. Couple that with the equinox which drives the tides even higher and welcome to Cozumel the end of March 2012.

The dive date was 03-28. The equinox 03-20. The new moon 03-22.

Do you know the tide times for the 28th...??

 

[vladimir]

Do you know the tide times for the 28th...??

Here you go:

Isla De Cozumel, Mexico

2012-03-28 12:55 AM CST 0.17 meters High Tide
2012-03-28 5:18 AM CST 0.15 meters Low Tide
2012-03-28 5:44 AM CST Sunrise
2012-03-28 12:05 PM CST 0.21 meters High Tide
2012-03-28 6:01 PM CST Sunset
2012-03-28 7:52 PM CST 0.10 meters Low Tide

A month earlier:

2012-02-28 2:04 AM CST 0.12 meters High Tide
2012-02-28 5:56 AM CST 0.11 meters Low Tide
2012-02-28 6:09 AM CST Sunrise
2012-02-28 12:52 PM CST 0.17 meters High Tide
2012-02-28 5:52 PM CST Sunset
2012-02-28 8:51 PM CST 0.06 meters Low Tide

An inch-and-a-half more water at afternoon high tide doesn't seem like a dramatic difference. The difference between high- and low-tide was the same.

 

[hypersonic]

Do you know the tide times for the 28th...??

No, but that would be interesting to know.

 

[Quero]

Here you go:

Isla De Cozumel, Mexico


A month earlier:



An inch-and-a-half more water at afternoon high tide doesn't seem like a dramatic difference. The difference between high- and low-tide was the same.

Cozumel doesn't get huge tides. Where I live we get much larger tidal flows, and it's such an important aspect of scuba diving here that we refer to tide table books throughout every dive day ("Phuket Tide Tables" ranks on the first page of a google search of "tide heights" that produces nearly 17 million results). Bathymetry has a big impact on tidal amplitude, and this map produced by NASA illustrates that the area where Cozumel is located is one of very low amplitude tidal changes:

​

The crazy Cozumel currents last month must have another genesis. The hypothesis that the crazy currents coincide with the equinox seems to be supported by this data analysis:

​

If this is indeed the case, it would seem that dive operators should be aware of this phenomenon and that it would be irresponsible to take inexperienced divers to walls during these periods of particularly turbulent and unpredictable currents.

 

[WSOPFAN]

A few thoughts on why the currents happen to be stronger or even dangerous at certain times. I am no expert on the subject but I would guess it had to do with the change of seasons and the underwater topography. I located this article and it has this to say:

Ocean current - Wikipedia, the free encyclopedia

An ocean current is a continuous, directed movement of ocean water generated by the forces acting upon this mean flow, such as breaking waves, wind, Coriolis effect,cabbeling, temperature and salinity differences and tides caused by the gravitational pull of the Moon and the Sun. Depth contours, shoreline configurations and interaction with other currents influence a current's direction and strength.

Many factors might contribute to a current at any time.

Surface ocean currents are generally wind-driven and develop their typical clockwise spirals in the northern hemisphere and counter-clockwise rotation in the southern hemisphere because of the imposed wind stresses. In wind-driven currents, the Ekman spiral effect results in the currents flowing at an angle to the driving winds. The areas of surface ocean currents move somewhat with the seasons; this is most notable in equatorial currents.

And they refer to surface currents as:

Surface currents are generally restricted to the upper 400 m (1,300 ft) of the ocean.

Over 1300ft are:

Deep ocean currents are driven by density and temperature gradients.

Also:

The movement of deep water in the ocean basins is by density driven forces and gravity. The density difference is a function of different temperatures and salinity.

Therefore it would be logical to conclude that what happens here has nothing to do with water temp or salinity and much to do with the surface current during the change of seasons and any other factor on that list individually or combined.

 

[Sorrows]

One thing I think we are pretty unanimous on is not to dive in conditions that are beyond your experience level. That's the clear message of the thread. It might not always be apparent where that line is, but if you are relying on the divemaster (where was your buddy?) for anything besides a dive briefing then you are a beginner diver, in my opinion, and you should avoid challenging conditions like strong current.

Excuse me, where and when did I say I was relying on the DM? I said the whole thing happened so fast that I didn't see how the DM (or anyone, for that matter) could have saved me--and I'm glad to say that my buddy was safely close to the wall; my problem (I think?) was that I swam a little too far from the wall and got caught in a downcurrent that everybody else missed.

I have 300+ dives, so yes, I have experienced strong currents before, but not that "washing machine" current. Blue Corner was nothing to it, IMHO (at least not on the days I went). So I would absolutely love to avoid those in future, if you can tell me where and when they are going to happen. I've been at Santa Rosa Wall a few times--and never experienced what the family in this video experienced. I dare say not many of us have.

And, btw, you certainly cannot rely on the DMs for the straight poop on current and conditions in Palau--there was a young woman doing her 2nd dive EVER at Blue Corner. Insane.

But thank you for the advice!

 

[vladimir]

Excuse me, where and when did I say I was relying on the DM?

Sorry. To be clearer, I should have said "if a diver is relying on the divemaster..." I also should not create the impression that my buddy habits are above reproach; they are not.

 

[InTheDrink]

... and sometimes how quickly you're descending can be deceptive, because you're in a moving frame of reference. I had to swim down and arrest the descent of someone dear to me a couple months ago ... in a mild downcurrent on a channel dive in the Maldives. She was fiddling with her camera while we were descending down a wall and didn't realize the current was pushing us down. By the time I caught up with her we were at 110 feet and falling fast. Grabbed her arm, showed her our depth, and we started swimming up hard. No telling when she'd have stopped if I hadn't caught up to her ... the bottom was another 300 or so feet below us.

There was some serious conversation going on when that dive was over ... mostly about paying attention to your descent and worrying about your camera once you get there ...

... Bob (Grateful Diver)

I've been to the Maldives a fair number of times now. Been in some pretty serious currents that just roll you over and can be quite fun. It's also where I started reef hooking - but always knowing I could cut the umbilical cord at a single slice (as I practised it prior to using it).

The Maldives is the only place I also came across a terrifying current. Maybe I wouldn't find it so scary now, now that I'm a little more experienced. But it went from nothing, to strong, to fierce, to completely ****ing mental in a couple of minutes. Channel & tide combo. Forget trying to stay with a buddy or anything vaguely similar.

I agree completely with the bit about fiddling with your camera once you've worked out where you are. Ascents and descents are times to be vigilant.

John

 

[dfx]

"Phuket Tide Tables" ranks on the first page of a google search of "tide heights" that produces nearly 17 million results

Maybe it does that for you, but not for the rest of the world. :tongue:

 

[mala]

Thankyou for posting the video (and separating it to it's own thread). As a new diver it was very eye-opening to see. We read about these things but there are few real-world visual demonstrations of what it's like. I certainly have learned a lot from both the video and comments.

I'm glad all three of you are ok.

I can't find the quote but it was said for the 2 divers at 165 the DM brought them up separately?? Am I wrong in seeing an issue with leaving a lone diver at depth waiting while another is assisted to the surface? Especially when there was a 'situation' in progress? I would think leaving a diver clinging to a wall at depth in an unmanageable(?) current is a big no-no.... Maybe I read wrong or am ill-informed of particular emergency procedures.

you should be asking yourself why the dm had no problems and most of the rest of the divers did.