Black Thermocline in quarry?

[SneakSnake]

My dive buddy and I recently attempted a dive at the Quarry lake in Sheboygan, WI. We have both dove quarries before, as well as cold water and poor visibility.

Vis was <10' at the surface. hit the first thermocline at about 18'. went to mid 50s F, vis was about 7'

As we descended, it got a little darker, but the most notable part of the dive was when we hit the 2nd thermocline, at about 30', water temp went to low 40s F. But it looked like a layer of ink at this level. It wasn't normal particulates that reflect light and bright lighting just makes it feel like high beams in a blizzard.

As we went through the thermocline, visibility dropped to nothing. Inches in front of the camera/light rig was the extent we could see. I put the light rig out in front of me at arm's length and turned it towards myself. These lights would usually be blinding, but it looked like brown points of light. 2x 700 lumen lights and an 84LED fill light were rendered useless. It felt analogous to what I would assume going blind and fumbling around in the dark with only the dimmest of shadow to guide your way around. it really felt like diving through thick ink.

Tried diving through it, but it kept going. With the quarry walls being mostly dark rock and having many outcroppings, we decided it was safest to not chance this.

My question is this: Have any of you seen anything like that? Is there a trick to diving something like this? even brighter lighting perhaps? I was seriously at a loss.

 

[Marie13]

Maybe a black sulphur layer. My local quarry in northern IL has a black sulphur layer that starts appearing later in the season. It just eats your light and you can’t see through it.

 

[Divin'Papaw]

I’ve seen that in quarries before in IN, IL & OH. Trick to diving in it? Keep a hand in front so you don’t run into something! Seriously though, when there is that much silt/tiny particles in the water column, there are no tricks. Light simply will not penetrate it. Either stay above it if possible or don’t dive it.

 

[GreggS]

One of the quarries I dive in NC used to have that in an area called the pit. Most of the quarry is 40 feet deep with rather poor visibility most of the time. The pit is a small area that goes down to around 65 feet. It has sheer wall drop offs on three sides but a more gentle slope on the front side. There is a line that you can follow down into the pit and which I had done but when you got to about 42 feet, the thermocline was the most stark I have ever seen. The temps would drop 10 degrees instantly. You could actually place your mask on the thermocline at eye level and and see light at the top of your mask and complete black at the bottom. As others have said, lights were useless below the thermocline.

2 or 3 years ago, the management placed aerators on the pit as well as a couple of other places in the quarry. The thermocline is now gone and the temps during the summer are usually 80 degrees from top to bottom. The pit is still dark but that's only because it is small and in a place where direct sunlight does not hit it well. It's more like doing a night dive during the day now.

 

[Divin'Papaw]

One of the quarries I dive in NC used to have that in an area called the pit. Most of the quarry is 40 feet deep with rather poor visibility most of the time. The pit is a small area that goes down to around 65 feet. It has sheer wall drop offs on three sides but a more gentle slope on the front side. There is a line that you can follow down into the pit and which I had done but when you got to about 42 feet, the thermocline was the most stark I have ever seen. The temps would drop 10 degrees instantly. You could actually place your mask on the thermocline at eye level and and see light at the top of your mask and complete black at the bottom. As others have said, lights were useless below the thermocline.

2 or 3 years ago, the management placed aerators on the pit as well as a couple of other places in the quarry. The thermocline is now gone and the temps during the summer are usually 80 degrees from top to bottom. The pit is still dark but that's only because it is small and in a place where direct sunlight does not hit it well. It's more like doing a night dive during the day now.

The pit in Gilboa can get black like this. The few times I've been down there it has been at least. Given that it starts at around 120-130' (I don't recall exactly), not many divers get down there. It is pretty small but it drops down another 10-15' I believe.

 

[boat sju]

Encountered this in a lake in southern Michigan once. Dropped through the thermocline and the lights went out. Blackest water I'd ever seen, and unexpected. I was unwrapping the line on our flag while following my buddy. He had his light out but I couldn't get to mine while dealing with the flag line which naturally found a way to wrap itself around my snorkel.

Anyway, fun dive. We figured it was tanic acid sitting on the thermocline that caused the issue.