In May of 1973, 8 divers were exploring a sinkhole in Australia
known as The Shaft when something went horrifyingly wrong.
This is their story.
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So the population distribution in the state of South Australia is really weird.
The largest city is the city of Adelaide with just over a million people,
but the next largest city is Mount Gambier at just 33,000.
This makes the second-largest city in the entire state over 40 times smaller than the next largest.
In fact, the population of Adelaide is larger than all of the rest of the cities in the state combined,
which is just kind of weird to think about.
And so, although Mount Gambier is technically the second-largest city in the state,
it's really just a small city.
Despite its size though, the city is considered to be the most important settlement
in the so-called Limestone Coast region.
It sits right on the border of South Australia and Victoria,
just a few kilometers north of the Southern Coast.
It also happens to have been built on the slopes of a literal volcano,
which is also named Mount Gambier.
Both the city and the surrounding area are famous for some of these volcanic features,
like the limestone topography, crystal blue lakes, caves, and sinkholes.
On the outskirts of the city are a bunch of farm fields,
and these extend all the way to the shores to the south.
One of these is just a small five-acre area (2 ha) between Mount Gambier and the ocean,
owned by some dairy farmers, and known as Thompson's Paddock.
In 1938, a farmer was on the field at Thompson's Paddock on a piece of equipment, being pulled by his horses,
when all of a sudden, one of his horses tripped and stumbled over something in the grass.
The farmer thought that was weird, so he stopped his horses,
got off the piece of equipment, and walked over to where the horse tripped.
What he found was a hole in the ground about a foot across that he hadn't ever noticed before.
He got down on his hands and knees to take a look into the hole,
and to his surprise, the hole extended for what looked to be at least 20 feet (6.1 m) down,
and then at the bottom, he could see water.
This on its own is kind of amazing and creepy, but this was only just the beginning.
It's not clear how long the farmer had had this field
or why he hadn't noticed the hole in the ground before,
and no one is really sure if the horse had caused the ground to collapse,
or if the hole had always been there and the farmer just hadn't noticed.
Either way, that leads to the next question:
If the horse had caused the hole to open up,
doesn't that mean that it could collapse even further,
and that the area around the hole was now at risk of collapsing?
To make matters worse, he could see from the surface
that the narrow opening extended for maybe two or three feet, but after that, the sides weren't visible.
It looked like it widened out, sort of like an upside-down funnel.
In a worst-case scenario, imagine someone had been walking in the field
and accidentally stepped into the opening.
They would've fallen 20 feet to the water below,
and then because of the shape of the upper section, they would've had no way to climb back out.
All they'd been able to do is tread water and scream helplessly.
This was obviously kind of alarming for their farmer as well,
because following the discovery of this opening, he decided to try to fill the pit with rocks.
So over the next little while, he began to bring soccer ball-sized stones to the opening
and just started dropping them into the water down below.
One by one, the rocks would make a big splash, and then disappear into the dark water,
never to be seen again.
They reached the first dozen rocks and they just kept disappearing.
Then, they dumped several dozen into the water.
The dozens turned into a hundred, then hundreds,
and there were still no trace of the rocks down below.
By the time they eventually gave up, they probably dumped thousands of rocks into the strange opening,
and still, not a single rock could be seen down in the water.
It was like the hole was bottomless.
In the end, the farmer would just had to be cautious of the opening
and hope that it didn't collapse any further.
As you might imagine, news spread of this weird occurrence,
and soon enough, people were coming to explore the hole.
It was eventually determined to be a limestone sinkhole
where slowly, the water had dissolved the rocks below,
leading to this large opening just a few feet below the surface.
Eventually, this foot-wide hole was widened to be about three feet or one meter,
so that could be more easily explored.
Then, in the mid-'60s, a diver was lowered into the cave opening for the first time.
From the surface, he was lowered 23 feet or seven meters
before finally touching down on the water's surface,
and what he saw was that it was actually more like a small lake.
Right below the entrance, it was narrow, but by the time you're at the water's surface,
the room is already 56 feet or 17 meters wide.
In addition to that, on a sunny day around noon, the sunlight shines directly through the opening
and creates a sapphire blue beam of light that lights up the room and the water.
From then on, the cave was given the name, The Shaft, because of this shaft of light.
From the water's surface, the diver began scuba diving down into the cave,
and found that it just continued to widen out the deeper and deeper you go.
In this first exploration, he got down to about 69 feet or 21 meters
before ending the dive and deciding to come back up.
But the craziest part was that from where he had stopped,
he could see all of the rocks that had been dumped into the cave years before.
All of those hundreds of rocks looked like a little anthill down at the bottom of this massive room,
and they were still at least 50 feet (15.2 m) from where he had stopped.
The cave was later mapped to have one massive chamber where the rocks were located,
and then two incredibly deep descending arms that extend out in almost opposite directions.
The main chamber is 460 feet long (140 m) and 260 feet (79 m) wide at its widest,
and the top of the rock pile is 118 feet or 36 meters below the surface.
Then, from the main chamber, there's a tunnel that extends northwest
to a depth of 260 feet or 80 meters.
And then on the opposite side of that, there's another tunnel
that extends all the way to 407 feet or 124 meters of depth.
It's thought that these tunnels could stretch all the way to the southern shores
as part of the intricate freshwater drainage system flowing through the mountains in the area.
There are also several cliffs, overhangs, and restrictions in each of these corridors
that make for some interesting features on the way down.
These features, coupled with the crystal clear water
and the sheer size to explore, make it a caver's dream.
Importantly, a really accurate map didn't get made until all the way in 1984,
but already by a decade earlier in 1973, 8,000 dives had already taken place inside The Shaft.
During all of those dives, the full depth of the cave wasn't known,
and a full map hadn't been made.
For all intents and purposes, it was considered to be bottomless.
The newness of cave-diving and limitations of the then available equipment
meant that cavers just sort of went to the edge of the charted area
and then stared off into the abyss, wondering how deep the cave went.
In May of 1973, a team of nine divers planned to make
what they thought might be a record dive in The Shaft.
On the 26th, they all arrived in Mount Gambier and set up tents
at a campground near the famous Blue Crater Lake.
Their goal was to reach the edge of the so-called Perimeter at 250 feet (76 m) of depth.
This is essentially the edge of where the light from above filters through.
Any deeper and the angle of the ceiling obscures the light,
and from then on, the water is almost pitch-black.
This also happened to be right around an area known as the drop off.
It's a point in the cave where the bottom is no longer visible from the edge above.
That's what gave The Shaft this reputation for being bottomless,
because standing at the ledge, you can't see anything down below,
but it clearly extends much farther.
All nine of the divers who planned to make this attempt were dive instructors,
but because this was a fairly ambitious undertaking,
they planned to do a practice dive and set up some equipment prior to their real attempt.
So the following day, on the 27th, they got to the farmhouse on Thompson's Paddock,
signed the guest book, and then drove into the grassy field where the entrance is located.
They parked alongside the opening and then set up the famous tripod hoist system
that many of you will probably be familiar with.
This hoist is used to lower the divers into the water down below,
and incredibly, despite having been widened,
the hole is still too narrow for divers to be lowered wearing their equipment -
it has to be lowered separately.
On the way up as well, a wire ladder is set up for the divers to climb their way out.
Once everyone was in the water, they were amazed
to see just how big the room was already at the surface.
Next, they set up something known as a shot line,
which is why they were there to do that day.
This was a line from the surface that was weighted and led directly down to the rock pile.
This would make their descent smoother for the record attempt
and give them more time to reach the edge.
On the practice day, the deepest they went was about 200 feet (61 m),
which was just around the perimeter of the rock pile and well within the light of the opening.
While they were down there, though, they could see the famous edge
off in the distance, which was their goal.
The bottom of the cave extended horizontally, and then just disappeared.
After finishing this practice dive and getting a feel for the cave,
they returned to Mount Gambier to replace some of the batteries on their lights
and refill all of their air cylinders.
Then, the next day, on the 28th, they were back at the opening at noon,
suited up, and getting lowered back down.
One of the divers, a woman named Joan, decided not to dive that day,
so it would only be eight of them instead of nine.
She decided to stay up and help with supplies and make food for the rest of them.
So the divers who would be entering the cave that day would be
Robert, John, Peter, Gordon, Larry,
and then three siblings, Glen, Stephen, and Christine.
The others all dive back down to the rock pile at 130 feet (39.6 m),
and then continue toward the tunnel where the ledge was located.
At about 180 feet (55 m), Robert started to really feel the effects of nitrogen narcosis.
This is when the nitrogen from the gas divers breathe dissolves in the blood
and creates a sort of impaired, almost drunken feeling.
This was a bit earlier than he normally felt it, but it was already significant enough
that he knew he needed to head back up a little bit to dissipate the feeling.
Now is maybe a good time to mention it
that because diving and cave diving were so new at the time,
the protocols used hadn't really been established like they are today.
There were a lot of amateurs who were participating in it who really shouldn't have been.
Like for example, these divers, although they were instructors,
they only had experience in open water in perfectly clear, bright water.
The second thing is that there was no requirement to be cave-certified.
Anyone could just sort of dive wherever they wanted with minimal oversight.
But the final and most alarming thing was that the safety protocols
were wildly different than what they are today.
This group of divers planned to do a dive to a depth of 250 feet (76 m) on regular air.
If you're at all familiar with diving, you know how insane this is.
Today, the maximum depth recommended to use regular air is just 130 feet.
Beyond that, nitrogen narcosis starts to kick in and can impair your judgment and motor function.
At around 185 feet (56.4 m), the air actually becomes toxic
and can cause convulsive seizures in some instances.
If you were to have a seizure at depth, your mouthpiece just falls out, and then you drown.
So taking all that into account, there were now eight divers in the water
on regular air already at 180 feet.
Robert signaled to the others that he was heading back to the rock pile,
and they signaled back to him that they were gonna keep going.
He then swam around the rock pile, circling it and checking the area
for animal bones that might have sunk into the bottom.
About eight minutes later, he saw Glen's torch coming toward him.
By then, Robert was close to being out of air, and so was Glen who had been watching his gauges.
The two of them caught up with one another, and then surfaced at around the same time.
Larry surfaced around the same time as well, and then 30 seconds later,
Peter surfaced and he had essentially no air left.
He also said that he hadn't seen any of the other divers.
All of a sudden, everyone's stomach dropped as their realization set in,
especially Glen whose brother and sister were still down in the water next to no air left.
A few minutes earlier, the group that had continued on without Robert,
were swimming and taking pictures until they got to about 200 feet.
Glen and the others were swimming along a ledge along the bottom,
and he saw his sister just a few feet away from him.
Everything was normal, the light above was still bright,
and about five minutes total had passed since they started their dive.
Around this time, Glen was feeling kind of groggy from the narcosis,
and decided that he'd gone far enough as well.
He checked his gauges and saw that he was getting low on air,
and knew that since everyone had the same amount of air, they'd also be running low.
To be on the safe side, he decided to head back up, but before he did,
he wanted to signal his sister, Christine, to let her know that she should probably head up too.
He went to tap her on the shoulder, but before he did,
she started kicking her fins away from him and then out of reach.
Not wanting to spend any more time down there,
he figured they'd probably all follow along not too long after him anyway,
so he just started up for the surface.
Then, he met up with Robert, and the two of them surfaced together.
Around this time is when all hell broke loose in the cave,
and a combination of factors led to this being perhaps the deadest cave-diving incident in history.
Right before Glen started heading up,
Peter was also feeling pretty impaired by the narcosis,
and wanted to check Glen's depth gauge.
He swam over to him, but Glen started heading up before Peter could read it.
Peter sat there for a moment, scanning the clear water at the bottom,
and then noticed two other divers moving towards the exit.
He checked how much air he had left, and that's when he realized that time was up.
Then, he turned to where he thought the exit was
and realized that the cave had gone almost completely dark,
and he had no idea which way the exit was.
That day, shortly after the group entered the cave, clouds moved into the area
and severely limited the amount of light shining through the opening.
Peter started swimming around, searching for the exit,
but in just a few short moments, the area had become heavily silted,
and the divers were scattered all over the place.
Three of these divers had been grouped together near the deepest section any of them had explored.
In order, Christine was in front, Gordon was next, and then Larry was in behind.
Larry and Gordon checked their gauges and realized they were dangerously low on air.
They signaled it was time to head up, and then in a panic,
started swimming almost directly upward rather than diagonally with the ceiling.
In these limestone caves, sometimes, pieces of rock cleave off
and create dome-shaped depressions in the ceiling.
It's thought that the expelled gases from the divers had collected in one of these pockets
and created a mirror-like effect on the ceiling,
similar to what the surface near the entrance would've looked like.
In their impaired state, their flashlights bounced off this mirror,
and in their panic, they thought they were swimming in the right direction.
Then, they would've swam directly up and hit the ceiling right above them.
Gordon and Christine started frantically waving their flashlights around,
terrified, looking for the exit.
Right then, Larry's light went out.
He dropped away from the ceiling for a moment and miraculously, it turned back on,
and because he had drifted down, he managed to see another diver off in the distance.
He swam toward the diver and then the angle was just enough
for him to see the real entrance far ahead.
He bolted for the entrance and surfaced right around the time Glen and Robert did.
Peter had also managed to find his way out of the silt and surfaced right after Larry.
Upon seeing that four people were still missing, including his brother and sister,
Glen immediately grabbed a spare tank and dove back down to try to find them.
He got to the edge of the cliff at 225 feet (68.5 m)
and found his brother's flashlight and camera resting on the bottom.
He also found that any further in was completely silted out - visibility was basically zero.
But desperately wanting to find his siblings,
he went over the drop off and into the silt.
As soon as he entered the cloud, he couldn't even see the hand in front of his face, and he started to panic.
He immediately swam back out and then to the edge of the rock pile,
and then he just stared into the abyss for some time,
hoping to see any sign of them.
Eventually, he was forced to return to the surface.
Peter went down following Glen's return, but he also found nothing.
By then, an ambulance had arrived and everyone knew there was no hope of finding anyone alive.
Shortly after that, police arrived and planned for a body recovery the following day.
The next day, police divers went down into The Shaft and got to 200 feet,
but found that the cave was still very stilted out.
They were already at the limit of their capabilities,
and weren't able to locate any of the bodies that day,
or the day after during a second search.
Following the second search, police called it off entirely
until they could get additional training from the Navy,
because the depth of the recovery was groundbreaking,
and pushing the edge of the training they had.
This would take at least several months to get their recovery squad up to speed.
In January of the following year, before the bodies had been recovered,
the landowners let a film crew who were making a cave-diving documentary,
enter the cave to do some filming.
The crew had already filmed several of the others in the area,
and wanted to include The Shaft as well.
On the 22nd, they got down to about 50 feet of depth, and using professional lighting equipment,
they lit up the cave so bright that it was like daylight inside.
While they were getting set up, a technician was looking at two of his teammates,
when he noticed what it looked like a third person behind them.
Kind of freaked out, they went over to inspect the area
and realized that it was a body in a wetsuit.
They immediately stopped all filming and surfaced,
and called the police to let them know someone had been found.
The next day, police retrieved the body, which was stuck under a narrow ledge
just 50 feet deep into the water.
They went down to 180 feet that same day and still weren't able to find any of the others.
The one they did recover was later determined to be Stephen - one of the siblings.
By March of that year, the landowners had become increasingly uncomfortable
that there were still three people somewhere down in the cave,
so they sought the help of some more experienced divers with better equipment.
On March 9th of 1974, this team of divers went down and began a search of their own,
and would find a person lying on their back at 185 feet on the bottom.
They also found another person directly underneath them.
Then, 20 feet deeper, they found the final individual -
the body of John beneath a rock ledge.
His body wasn't able to be recovered until a month later in April
because of the depth and the way the body was wedged.
Almost a year earlier, on that fateful day,
it's thought that Christine and Gordon had run out of air
while in the dome-shaped pocket on the ceiling.
It's been suggested that they died holding one another,
knowing they were out of air and there was nothing they could do.
This is why they were recovered so closely together.
It's not clear exactly who saw John, but one of the survivors mentioned seeing
another diver swimming strongly and deeper into the cave
while everyone else was returning to the surface.
This is thought to have been John who was found the deepest in.
It's thought that he was severely affected by nitrogen narcosis,
and that's why he was going in the opposite direction.
Finally, not much is known about Stephen's final moments.
He was obviously found much higher than the rest of them
along the ceiling instead of the bottom.
When he was found, his buoyancy device was inflated,
which kept him buoyant and stuck to the roof.
It's possible that in the silt or in the dark, he tried to find the exit
by floating to the ceiling and then crawling along it.
He might have then run out of air before making it out.
However, since no one saw him, we'll never really know his final moments.
This accident, as far as I can tell, is the worst in cave-diving history.
And in the few years preceding this incident, there were several other fatal incidents
in nearby sinkholes in the Mount Gambier area.
The Shaft disaster was the final straw
and led to the establishment of the Cave Divers Association of Australia,
with the goal of regulating the industry to prevent further tragedies from occurring.
With the benefit of hindsight, we know that these divers should not have entered the cave
without specific knowledge of cave-diving.
It's also easy to criticize their use of air instead of a mix,
but back then, specialized gas mixtures just weren't widely available.
They also should have used guide lines to explore those uncharted sections
to avoid getting lost when the cave silted out or when it became dark.
And in fact, these divers knew that lines should be used,
but decided not to use them because of the size of the group they had.
They knew that the lines would likely get tangled, which would've been even more dangerous.
In reality, for a dive like they did, they should have simply had a smaller group
where lines could have been used.
Thankfully, following the establishment of the CDAA and other similar organizations,
the rate of cave-dive deaths has been drastically reduced ever since.
Hello everyone. My name is Sean, and welcome to Scary Interesting.
Thank you all so much for watching, and hopefully, I will see you in the next one.