Coming up next on Jonathan Bird's Blue World,
Jonathan dives a really deep and spooky blue hole in the Bahamas!
All of this today on Jonathan Bird's Blue World!
Hi, I'm Jonathan Bird, and welcome to my world!
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Everyone knows that the Bahamas have beautiful beaches and lush coral reefs. But they're
also world-renown for cave diving. And in the Bahamas, cave diving usually means blue
holes.
In particular, the island of Andros has dozens of blue holes, clearly visible from the air.
Walking through the forest here on Andros, you can see that the forest floor is the remains
of an ancient sea bed. This limestone was formed by coral reefs millions of years ago.
Rain, combining with carbon dioxide in the atmosphere creates mild carbonic acid---otherwise
known as acid rain—which slowly dissolves limestone.
Millions of years of rain falling on this rock and then draining in, have slowly dissolved
away the rock, creating these odd little crevasses and holes. And it has made the whole floor
of the forest look like a gigantic piece of Swiss cheese.
Some of the holes have gotten pretty big. I mean this one is the size of a hot tub.
But in a few places, the holes are enormous, and full of water. These are the Blue Holes.
It's easy to see how the blue holes got their name. Andros is covered in them. They look
like circular ponds from the air, and often lead into vast underwater cave systems.
I have teamed up with Small Hope Bay Lodge and divemaster Mike Hornby to explore The
Guardian, one of the more famous Blue Holes on Andros. It's a hike through the brush
to get there.
MIKE: We have about a quarter of a mile we are going to have to carry our gear in.
JONATHAN: I gotta walk all the way in here in my full scuba gear?
MIKE: Yep!
JONATHAN: Oh man!
MIKE: Well, we don't have too far to go. We're just about ready to round the corner
and it's going to open up into a beautiful blue hole. OK, Jonathan, here it is. This
is the Guardian Blue Hole!
JONATHAN: Wow! It doesn't look that blue.
MIKE: If you look off in the distance there and you see that little bit of an archway,
that is going to lead into one cave system, and right down here, this is the entrance
to our other cave system.
JONATHAN: So this is where we're going down?
MIKE: Yes. So the Guardian blue hole is the portal for the cave systems that lie underneath.
So, I head back to get my camera.
This is a lot less convenient than boat diving.
It takes several trips to get my camera, plus all the other gear, to the water.
What I want to know is who was the first guy to discover this muddy hole and say "Hey,
this would be a good place to go for a dive!" I mean, look at it.
Back at the truck, Mike and I start suiting up. We will walk in our gear to the water.
Mike, as a cave diving instructor, will be my guide to exploring the blue hole. Mike
wears some specific gear for cave diving, including redundant dive computers, an extra
regulator and he will even be carrying a spare scuba tank.
So I'm not quite as technical as Mike, but I do have some specialized gear for cave diving.
I have a scuba tank, it's a normal scuba tank, but it has an H valve on it. It has
two separate independent first stages. So I've got my normal regulator that I always
use on the first one and a completely separate, redundant backup regulator on the other one.
So that way I can turn one off, turn the other one on, and if I have a problem with either
one of my regulators, I have a completely secondary backup. For lighting, my lights
on my camera, my huge video lights, those are my primary lights. But I have a flashlight
in my pocket and a chemical light stick which you break and it glows and you have 12 hours
of light. It has no batteries and that's probably more lights than I'm going to need.
With our gear all assembled and ready, we hike into the brush. And man is it hot! Nothing
like a long walk in the hot Bahamian sun wearing full scuba gear and a wetsuit to burn off
a few calories!
MIKE: This water is going to feel extremely good after that warm walk through here.
JONATHAN: Oh yeah, I'm looking forward to that!
Finally it's time to jump into the water and explore the Guardian.
JONATHAN: Oh that feels so good!
Well, it's time to go check it out!
As I sink down into the yellowish-green water, I can hardly see because it's so murky.
I'm following Mike's pink fins. He specifically uses the brightest pink he can find so the
people following behind can see him in limited visibility.
Cameraman Tim is right behind me, bringing up the rear as we sink down into a dark spooky
hole in the ground.
As we descend, we pass through layers of what looks like smoke in the water. Mike points
out these clouds of suspended sediments to me as we keep sinking.
The blue holes leads into a huge cave system and it's a lot deeper than you might imagine.
Periodically Mike turns to make sure we are still here, and his flashlight illuminates
a permanent guide line that previous divers have installed. This line guides the way out
in case we get disoriented.
The walls on each side of us go straight down. We are sinking into a deep crack.
As we get deeper, the walls get closer together, but the water gets clearer. We have passed
into seawater from the freshwater above. I can taste the salt on my lips. If we could
go far enough, eventually we could reach the ocean.
Mike points to ancient fossilized seashells imbedded into the limestone. Here's a conch
shell.
Our bubbles are hitting rock overhangs and knocking off sediment which is raining down
around us, reducing the visibility.
I continue to follow Mike, until finally at a hundred and fifty feet deep; we reach some
stalactites in a formation called candle wax. These were formed by dripping water during
the last ice age when sea levels were much lower and this part of the cave was dry.
Down below me, it's more than 500 feet deep in this cave. I don't think we'll be going
down there!
We turn around and start heading back, with Mike continuing to point out fossils.
Following our guideline back into the shallower, murky water, Tim is right behind me.
And Mike, with his spare scuba tank slung under his arm, is right ahead.
Periodically, markers on the line point the way out. These can be used in the event of
a light failure to feel your way to the surface.
At last we can see the dim glow of daylight from above as we ascend towards the sun.
Back in the shallows of the blue hole, Mike shows me around.
The bottom looks like its sand, but it's actually a deep layer of silt.
While Tim hovers high above the bottom to keep from kicking up the silt, I perform a
little experiment.
Down on the bottom, I plunge my arm into the silt up to my shoulder and it's even deeper
than that. This is a layer of decomposing leaves and other organic stuff. The decomposition
creates hydrogen sulfide, a deadly gas that smells like rotting eggs. The water is saturated
with hydrogen sulfide and I can smell it in the water that seeps around the edge of my
mask.
Wow. That dive can only be described as spooky. The water is kind of colored like mustard,
and you can't really see where you are going, and it's all swirly and if I wasn't following
Mike I would have been totally lost. That dive was very spooky but really interesting.
The next day I'm out on the ocean, suiting up for another dive. Mike has something he
wants me to see. After the last dive, I can't imagine what crazy thing he is thinking now!
I roll into the water and follow Mike and his trademark pink fins down to the reef.
Then we keep going down into a cavern below the reef.
At the bottom of the cavern, Mike points to a hole and motions for me to go in ahead of
him. Once again, it's pretty spooky, but exciting at the same time. So in I go, with
Tim and Mike right behind me.
Inside, it opens up into a big cave. We're not deep enough for stalactites though.
As we come around a corner, I look straight up to see light coming in from above through
a huge crack in the rock.
We make our way right up the fissure into the blue above.
I'm in an ocean blue hole, formed just like an inland blue hole 20,000 years ago during
an ice age, when the ocean levels were much lower. Once the ocean levels rose, this blue
hole ended up underwater.
But this blue hole connects through a vast labyrinth of caves to the inland blue holes.
And as we emerge into the open ocean, something looks weird.
When the tide goes out, all the water from inside the caves gets sucked out into the
ocean, bringing with it silt and hydrogen sulfide from the inland blue holes! It forms
clouds near the bottom, with a distinct line between the clear ocean water above, and the
silty hydrogen sulfide layer below. What you are seeing here are the decomposing remains
of forest vegetation which have passed entirely through the caves and out into the ocean!
Everywhere I find what look like strands of mucus floating in the water. It's most likely
mucus secreted by the coral in response to the caustic hydrogen sulfide.
It's stuck on everything, including this gorgonian, which has closed all its polyps
to protect itself from the hydrogen sulfide. As the tide carries the toxic water away,
the corals will go back to normal.
Finally, we head back to the boat. Tim and Mike hang on to the anchor line to do a short
safety stop before we surface.
My exploration of the Guardian blue hole on Andros was both fascinating and a little spooky.
But I have to admit I'm intrigued. There are quite a few more blue holes on Andros
for me to explore, so I'll be back!
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