Escaping Down Drafts

[lermontov]

I've been reading about people caught in downdrafts, Ive never been in one but can anyone give me data on the conditions for one too exist - is it geographic, tidal, combine i particular environment how wide are they, best technique for escaping, do they give any clues on surface to there existence ?

From what I've read they appear to be conditional on topography ? and is it more aggressive on tidal flow?and best practice to escape is get neutrally buoyant and swim (tack across) yes?

 

[CuzzA]

I think you're right the topography of the site plays a significant rolls as well as tides, currents, thermoclines.

As for how to survive one, I don't know the textbook answer, but logic tells me to not excessively fight it physically as you'll likely over breath your reg and exacerbate the situation. Of course doing nothing could send you to the abyss, so I would think you would first want to focus directly and continuously monitor your depth gauge, get vertical to reduce drag, continue to kick up and power inflate, but be ready to dump to avoid an uncontrolled ascent and by all means keep your airway open.

 

[Diving Dubai]

I put a long post in this thread

The theory states you swim out from the wall or rock where the current is. In practice not always possible

But from my actual experience (and we get down currents on our dives every couple of months or so)

Down currents are normally recognised by your ears hurting as you get pushed down fast. Yes you are supposed to swim away from the wall out of them. Hard to do as your mind doesn't always work that fast. Get you equalisation sorted and add air to your BCD but be ready to dump and keep an eye on your depth gauge so you know which way you're going. The last one I encountered 2 weeks ago slammed me and my buddy down 22m (60') before we got out. But that's why as a standard we carry a 40cf of air - in case we're pushed below our MOD

The trick isn't to make yourself buoyant, you just need to minimize the ride down. You don't want to be filling your BCD to its max capacity - Get control. hard if you're inflating with one hand and equalizing using the other. If you can grab on to a rock and hold on while you sort your self out.

Most can be very small, you might get pushed down a little but as you start finning you're out of it.

Be conscious of your gas. You're breathing rate can double. Get stabilized and then look for a way out. Before now I've "climbed" diagonally upwards across the wall until I can get out. A fully inflated BCD/wing can be no match for mother nature.

Reef hooks and gloves are your best friend

These kind of currents are normally found in specific places, Indonesia is famed for them. a good dive brief should make you aware of any possibility - although mother nature is kinda fickel and doesn't always play by the rules

 

[MXGratefulDiver]

It depends on the type of downdraft ... they're not all the same, nor caused by the same types of currents. The most "famous" ones, in terms of recorded incidents are probably on Palancar Wall in Cozumel. These are like submerged waterfalls, and tend to push you down the face of a wall. As DD stated above, if you can swim far enough away from the wall you can generally get out of them. The risk, of course, is that they're not as localized as you think they are (and you can't really tell), and it pushes you into the abyss as you try getting away from it. I'd think a less risky approach would be to swim "into" the wall and find something to hang onto or even to pull yourself up. Currents tend to decrease when you get very close to structure, and in any case hanging on won't make you go any deeper. These currents are usually transient, and in a few minutes can disappear altogether. And if you're holding onto something you won't be working so hard, and therefore not sucking through your air so fast. Yes, I know it violates a basic "no touch" principle ... but diving's a situational activity, and in situations like this you have to sometimes "break the rules" in order to survive. Prioritize your risks.

At my local mudhole we have a well-known phenomenon known as the "Redondo River". It's a strong transient current ... usually occurs during periods of a large ebb ... that can pull you downslope at times. A few years back we lost a diver when she tried swimming upslope in the current and ran herself out of air. Again, a better approach is to get low to the bottom and if possible find something to hang onto until it passes ... usually only takes a few minutes. Or you can try swimming parallel to it (crabbing), but if you guess wrong and swim the wrong way you'll only be tracking with the current as it moves down the beach. I've experienced this current many times, and often there are several minutes of "warning" as the current goes from mild to wild. If you're aware of the building current you can use that time to get yourself shallower or find some structure to duck behind to get out of it. The key is to put yourself into a situation where you don't have to work hard and therefore suck through your air too quickly.

The other option is to swim upward, filling your BCD as needed to gain enough buoyancy to overcome the pull of the downwelling. This is risky, and you really have to pay attention so you don't become a cork when you do break free of the current ... it's something I'd consider a last option. The best approach is to hang on and wait it out, paying attention to your available air supply so you don't run yourself out of gas before you run out of options.

... Bob (Grateful Diver)

 

[lermontov]

I. These currents are usually transient, and in a few minutes can disappear altogether.


... usually only takes a few minutes. Or you can try swimming parallel to it (crabbing), but if you guess wrong and swim the wrong way you'll only be tracking with the current as it moves down the beach. I've experienced this current many times, and often there are several minutes of "warning" as the current goes from mild to wild. If you're aware of the building current you can use that time to get yourself shallower or find some structure to duck behind to get out of it. The key is to put yourself into a situation where you don't have to work hard and therefore suck through your air too quickly.

The other option is to swim upward, filling your BCD as needed to gain enough buoyancy to overcome the pull of the downwelling. This is risky, and you really have to pay attention so you don't become a cork when you do break free of the current ... it's something I'd consider a last option. The best approach is to hang on and wait it out, paying attention to your available air supply so you don't run yourself out of gas before you run out of options.

... Bob (Grateful Diver)

so its a kind of underwater avalanche and width is unknown until you find the edge ?I imagine its like a sea rip but downwards?

 

[Kevrumbo]

Downcurrents can be the worst dilemma any diver can face especially if you've got Nitrox MOD limits to consider as well being pulled down: the more you exert against the downdraft; the harder you breath & use up gas; CO2 retention-Narcosis/Hypercapnia sets in and increases the chances of Ox-tox hit as you approach & go beyond PO2 MOD limits if you cannot arrest the descent. Last resort if in blue water with no reef wall topography to climb back up is to inflate BCD and make your way up without overexertion as best you can. . .

 

[TMHeimer]

All great advice, though I have yet to experience one. Hope not to.

 

[vincent54]

To avoid a down current,
1) Know your dive site. Ask locals who dive the area.
2) Know your tide schedule
3) Keep an eye on the wind and swell
4) Watch floating debris. If it is moving, adjust accordingly.
5) Know your limits. If you think you can't do it, Don't.

The down currents I've been in, there is always some warning. There is a site(just east of Burt Brother's Boulders) I dive that generates a strong down current as the water moves around a limestone outcropping. It's always there after a day or two of a steady wind and swell. You see everything going over the edge, sea weed, plastic and sometimes people

About a year ago, I had a new diver friend not follow my advice and went seaside to the formation and shot down to about 160 feet in seconds. He would be dead if the flow didn't peeter out at depth. Basically he ended up out in the abyss, past the outcrop. I don't recall asking if he added gas to BC, but he must have the way he bobbed up. After swimming back to me, he was out of gas, and looking scared to death. The whole episode lasted less than a minute.. I gave up the octopus and we ended the dive draining the rest of my tank before we hit shore. I was panicked watching him, he was panicked and it was a good old fashioned cluster f#$%. In conclusion, don't get into one.

 

[TMHeimer]

I've always said that everyone has a panic threshold no matter how experienced. Something like that very well may push me over mine. As pointed out by many, if a site is new to you (and especially if it could be suspect), get a local orientation.

 

[NYCNaiad]

I was caught in a down draft in a whirlpool in the Maldives. I was not near a wall. I got caught in it while trying to come up after my safety stop. It was very confusing at 1st. I couldn't understand how the boat overhead was getting farther away when I was swimming upwards. My bubbles streaming straight down clued me in. I immediately checked my depth & found I was already down to 77ft. (This all happened very quickly & occurred after I aborted a dive when the current picked up drastically.)

My safety sausage wrapped around my legs & it didn't even occur to me to use my knife. I got panicky & had no prior knowledge of what to do to get out of a down current. (Good for you that you're asking the question!) I blew up my BC & tried swimming up...eventually I figured out I had to swim perpendicular to the down current....sideways, not up. I got out of the current, but wasn't prepared to dump the air from my BC so I shot to the surface. Luckily, I experienced no health issues. Side note: I never noticed the pressure changes in my ears as I was sucked downwards until after the dive when my ears were sore.

All of this took very little time. You'd be shocked by how quickly it can happen & then be resolved one way or the other. You won't have a lot of time to plan or think.

The things to keep in mind are:

• Don't panic; you can survive this.
• Swim sideways, not up.
• If there is a wall & you are next to it, grab hold. If you have to, you can also use it to climb up or sideways once you get your breath back. Don't worry about the coral or marine life. Your safety is more important. (This helped my dive group who were caught in the same current I was.)
• If you're still going down, put air into your BC, but be prepared to dump the air quickly once you're out of the current. If for some reason this doesn't happen & you begin to pop up to the surface, remember to breathe out continuously so you don't seriously injure your lungs.

Down currents don't happen often, but it's always good to have the knowledge of what to do if you ever get caught in one.