Downward currents?

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A couple weeks ago I was diving with a buddy from my club, one of my first times doing so outside of our organized club dives and at a location I'd never been. The site itself was great, and the person I went with was a great buddy. While down at about 55ft we hit a really strong lateral current which would have been very difficult to fight. It swept us along quite quickly which we took advantage of for a bit, then ascended about 10 to 15 ft to escape it. All went well and we finished our dive at a more shallow depth, finished up and headed home.

I'm currently AOW with 36 dives, though I did my OW 3 years ago. If they mentioned anything about currents then I've long forgotten it, as they've never been an issue at the spots we usually dive. My biggest concern (especially here in BC, where there are some tremendous vertical drop-offs) is hitting a downward current and not knowing what to do. Do these exist? If so (I'm almost positive I've read about them here before), what's the procedure to escape them calmly and safely?

Yes, and they exist in places you are likely to dive someday. One of the most notorious places for downcurrents in your area is Quadra Island, which is known for current (fantastic diving, though). I've also hit downwellings at Race Rocks, just off of Victoria.

... Bob (Grateful Diver)
 
There is a dive in Komodo National Park that they call "Washing Machine." (I'm sure there are others with the same name.) From the skiff we could see clear signs of turbulence on the surface where our dive would end: eddies and flat areas with no ripples. We motored a short way further and dropped in to a gently sloping reef and a mild current. Following the instructions from a detailed dive briefing, we maintained our depth around 50 feet as we approached a clearly defined ridge. The current accelerated noticeably as we neared the ridge and all the fish were oriented towards the depths. At the instant we traversed the ridge a strong vertical current swept half of us up to 25 feet and the rest all the way to the surface. Three of us, including our guide, took refuge in a little niche in the reef. It was amazing that you could actually stick an arm out from our little alcove and feel the fierce current outside. Just a few meters further along on the reef the current was equally fierce in the opposite direction, and we swam into it and had a quick elevator ride down to 90 feet, where 3 reef sharks swam in a circle and the current petered out. It was a great dive and a great experience, but if it had happened without any warning it would have been scary as hell. As it happened though, it was more like an amusement park ride.

I remember that place ... when we finally surfaced I just wanted to scream "YEEEEHAW ... WHAT A RIDE!" ...

... Bob (Grateful Diver)
 
Yes, and they exist in places you are likely to dive someday. One of the most notorious places for downcurrents in your area is Quadra Island, which is known for current (fantastic diving, though). I've also hit downwellings at Race Rocks, just off of Victoria.

... Bob (Grateful Diver)

Is Quadra known for downwellings or heavy currents? If it's downwellings then where is the current coming from? I could only really visualize it happening from big tidal flows out of Georgia straight at spring tide. Is that what happens or is it a daily thing?

I know at the mouth of Sechelt Inlet there's a place (something like Skookumchuck narrows or something...it's been a long time) with rediculous currents too but they aren't really downwellings. It's more like being flushed down a toilet.

R..
 
I've not hit downwellings at Quadra but have experienced the washing machine thing but from side to side...you couldn't leave the wall and were just pushed from side to side...fun though but no depth changes. Not saying they can't occur there though.
 
Is Quadra known for downwellings or heavy currents? If it's downwellings then where is the current coming from? I could only really visualize it happening from big tidal flows out of Georgia straight at spring tide. Is that what happens or is it a daily thing?
Heavy currents always ... downwellings sometimes, especially at places like April Point. When Cheng and I were there we hit one particularly bad one that ended up pushing some divers well down the wall. Grabbing a handful of kelp stems can help sometimes ... depending on where they're anchored. But kicking out away from the wall is usually the best option, if you've got time. Watching the orientation of the fish can give you a fair amount of warning. When they start swimming "up", it's time to head away from the wall.

I know at the mouth of Sechelt Inlet there's a place (something like Skookumchuck narrows or something...it's been a long time) with rediculous currents too but they aren't really downwellings. It's more like being flushed down a toilet.

R..

I'm only familiar with Tzoonie Narrows in Sechelt inlet, which has one particularly well-known upwelling (because of a strategically-placed house-sized boulder), but downwellings aren't a problem there. It's fairly shallow (70 fsw or less) in any case.

... Bob (Grateful Diver)
 
*sigh* I really miss diving in BC. This is making me sad :sad2: I'll only get one or two dives in this coming vacation and it's for catching crabs for the party we're planning...

R..
 
I've seen three different sorts:

  1. Actual downward flow of water, usually in the topics, usually driven by a salinity difference where saltier water built up behind a reef or in an atoll and was then brought out by the tide into less saline water.
  2. Buoyancy weirdness brought on by moving from a saline to a fresh situation (or vice versa) as in a kettle hole, freshwater spring or estuarine salt wedge, at the extreme you can suddenly have a shift of as much as 4% of your buoyancy.
  3. Buoyancy weirdness brought on by moving from:
    1. a denser water mass (e.g. heavily silted) to a normal water mass.
    2. a normal water mass to a less dense water mass (e.g. strongly aerated with lots of small bubbles).
 
I did not want to mention this one, but as long as we are talking about tornados...

A friend of mine was diving the same site in Cozumel where I encountered the down current (Jucab Wall). She and her buddy ascended a little ahead of the others and were doing their safety stop. Suddenly they started swirling and descended rapidly. then they were at the surface. Their computers showed that they had gone to 100 feet. Then the rest of their group surfaced, and they had experienced the same thing. The visibly shaken DM took everyone straight to the chamber for evaluation, but everyone was OK.
 
Here's a different take on what a downwelling can do ... this occurred about this time last year at my local mudhole. We've since encountered this same current several times ... and named it the "Redondo River" ...

Miso Soup:
July 9, 2008

Sometimes the most interesting dives are the ones that don’t go according to plan. Cheng and I had an interesting one at Redondo recently.

I’d been having consistent luck finding lumpsuckers down in the seaweed beds between the carousel boat and bottle field … not to mention finding all sorts of other interesting “small stuff” like unusual nudibranchs, small octopus, the occasional stubby squid and grunt sculpin. But with the lumpsuckers, in particular, none of my pictures were coming out … mainly because they were all really tiny ones, and sitting on a piece of seaweed that’s gently moving all the time poses certain challenges with a point-n-shoot camera.

We entered the water on a really low slack … the tail-end of an 11-foot ebb going into an equally large flood. But Redondo’s usually pretty user-friendly, so we weren’t too concerned. The tide was very low … we finned up while literally standing on the edge of the drop-off. There wouldn’t be much of a surface swim today … we kicked out about 30 feet and dropped.

Going downslope, I found the tiniest mosshead warbonnet I’ve ever seen … maybe an inch long. We stopped and took a couple pictures, and proceeded down toward the carousel boat … I was a man on a mission, after all. Further down the line we came upon a couple of grunt sculpins .. one of them quite orange and pretty.

Vis wasn’t very good … but that’s about normal on a very low tide. At the carousel boat we looked for the octopus that’s been denning under there, but apparently it wasn’t home. Or at least, it wasn’t visible by peering under the boat. So we turned south and headed through the seaweed bed toward the bottle field.

We hadn’t gone very far when I found what I was looking for … a tiny lumpsucker, so tiny it more qualified as an insect than a fish. I got Cheng’s attention and moved back a little bit so she could get a picture unimpeded. She took a couple shots, then motioned for me to have my turn. As I was setting up the shot, I noticed a lot of seaweed getting kicked up. A little annoyed, I turned to motion for Cheng to stop kicking … and then noticed that she was hovering perfectly still, a little bit down current from the subject … right where she was supposed to be. So what was kicking up all the seaweed? Looking upslope, into the current, I couldn’t help but notice a literal wall of seaweed moving toward us … fast. About all I had time to do was signal Cheng, point toward it, and move closer to her. Then we were enveloped in a literal maelstrom of flying seaweed and current. Flying bits of seaweed were sticking to my mask, and visibility went to zero in a hurry.

We both reached out and grabbed each other, holding hands as the current kicked both us and the seaweed around. To say it was disorienting is an understatement … I know I lost all sense of direction, and I’m sure Cheng did too. So I pushed downward on her hand and released all the air from mysuit and wing … hoping she would do the same (she did). We felt … but did not see … the bottom.

Well … I thought to myself … this is good practice. I’m trained for it, but she’s not. We’ve done a lot of dives together, so let’s see where it goes. Tugging on her hand, I guided her in the direction I thought would get us back to the carousel boat. She squeezed my hand back (OK) and pushed in the same direction (she understood what I wanted to do). Clinging to each other’s hands, we literally crawled together … not being able to see a thing past the inside of our masks. Within a minute or so we literally bumped into the side of the boat. Feeling our way to the bow, we found the guide rope that would take us back upslope. Once on the rope, life felt good indeed … I knew that as long as we didn’t lose it we wouldn’t need to see … it would take us home.

By the time we got back up to 50 feet, the current had slowed down and the seaweed had thinned out to the point where we could at least let go and wipe our masks clear … we could see the rope and parts of each other. The current was still running downslope, but at a much moderated pace … one we could easily deal with. At about 30 feet the current reversed, and gently pushed us upslope. At 10 feet it quit altogether.

When we surfaced, everything around us looked completely calm. We were a bit baffled by what we’d experienced until we looked further out, where we could see a line of ripples running like a river … bracketed on both sides by glassy calm water and moving steadily away from shore.

Getting out of the water was downright comical … we were covered head to toe in seaweed … two “swamp things” emerging from the deep. As we headed off to the showers I remarked to Cheng, “what the heck was that, anyway”. Her response was typically Cheng … all she said was “miso soup”.

... Bob (Grateful Diver)
 

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