Tourist lost - Cozumel

[Trailboss123]

Kimela, for what it is worth:
I have more than a thousand dives on Cozumel and my primary diving is for Lionfish and for the last few years that means over the wall and relatively deep. I have thought about this for a while and have my own theory which may or not be correct.

The channel current near Cozumel is one of the fastest around at 5-6 KTS, the current is not fixed but has slight variations in both velocity and direction. The channel is wider in the south and the near shore shallow current is typically northward being drug along by the main channel current but typically much slower. Below Cedral the island shore is more north / south and the channel is wider, above Cedral it shifts to NNE (about 30 degrees) while the mainland is more ENE (about 60 degrees) causing a constriction. The near shore current in the south (which extends to the reef) continues its N direction past Cedral point where the shore angles more east. This mass of water moving in relatively slow current typically causes a slight off shore current near Santa Rosa but the amount of energy involved in even a slow current is massive.

In the winter and spring months the main channel current, I suspect, wobbles in direction and causes eddies often seen as reverse currents all along the reef, it is referred to locally as 'crazy currents' and it normally occurs from late January thru May but especially in late February and March, but can happen any time. In the case of Santa Rosa there is already a slight off shore current from the southern shore current and the wall is very shear. When a main channel eddy collides with the remnants of the southern shore current the pressure has to relieve itself somewhere and the path of least resistance would be downward over the shear wall of Santa Rosa. I have see this from from mid Cedral thru Santa Rosa.

I have been seen a lot of down current at various points along the reef and watch closely the sand shoots between sections of the reef. These sand shoots are the pressure relief points and points of least resistance and if I see turbulence, ‘dust devils’, on the sand I go either high or out to avoid any down drafts.

For what it is worth that’s my best guess.

Very well stated Gary.

 

[Cozdreamer]

God Bless the diver and the wife and those onboard and crew and extended family...My heart breaks.....

 

[auto]

One whistly on DSMB, One whistle with mirror in dive shorts, along with small light with strobe.

 

[Johnoly]

.... and watch closely the sand shoots between sections of the reef. These sand shoots are the pressure relief points and points of least resistance and if I see turbulence, ‘dust devils’, on the sand I go either high or out to avoid any down drafts.

Perfectly stated @gopbroek !!...As you are gliding along and see the open sand shoots approaching, you can very clearly see the sand turbulence pushing downward. It's pretty easy to avoid them.

 

[blue steal]

I am trying to understand how a down current can affect you at a 5-6 meter SS.
I always thought they happen on or below the wall.

 

[DandyDon]

I always thought they happen on or below the wall.

That's my understanding. Currents meeting on top of a wall forces a downwelling in front of the wall.

 

[Biotech Diver]

Do y'all carry signal mirrors? I wear one hung from my neck inside my jumpsuit. Can be seen a lot further than a horn can be heard, which I also carry.

I always do. I also carry a Garmin In Reach, a whistle, and of course an SMB. I’ll probably add a Nautlis to my gear as well because the one concern i have with the Garmin is it’s not rated to be submerged more than 6 feet i think and Garmin doesn’t claim it to be waterproof. Maybe the solution is a housing that lets you activate it without opening it?

 

[DandyDon]

I always do. I also carry a Garmin In Reach, a whistle, and of course an SMB. I’ll probably add a Nautlis to my gear as well because the one concern i have with the Garmin is it’s not rated to be submerged more than 6 feet i think and Garmin doesn’t claim it to be waterproof. Maybe the solution is a housing that lets you activate it without opening it?

I am not well versed on the InReach line, but I understand them to be "water resistant to one meter for 30 minutes." That's without any movement that would add pressure. There is a dive case for the InReach Mini, but you'd have to remove it from the case on the surface to use it, and not drop it. I carry a buoyant PLB. You need to research InReach looking for solutions.

 

[Thunder Struck]

Ditto - I just ordered the storm whistle after reading this thread and am reassessing my octo location.

Another Storm whistle purchased.

 

[tridacna]

Curious. Frank @Wookie , how effective are these whistles in your experience?