- [Narrator] Jacob's Well in Texas is one of the best places
to swim on a hot day.
But below the water's surface
lies a dark and dangerous network of caves
that are so deadly, this spot's been labeled
one of the most dangerous diving spots on Earth.
So what exactly makes the underwater caves of Jacob's Well
so deadly?
(static warbling)
Let's find out on today's episode of--
- [Announcer] "Colossal Mysteries."
- [Narrator] Jacob's Well in Wimberley, Texas
seems like any another tourist attraction
you might find while traveling around the country.
The natural spring is full of perfectly clear
and cold blue water that looks quite exotic.
Underwater is a well that's about 13 feet wide.
The natural spring was uncovered by settlers in 1850.
As you might imagine,
finding a pool of clear, (settlers clamoring)
crystalline water that would sometimes spout water
several feet high in the middle of sunny,
dusty Texas was quite a find.
Ever since, Jacob's Well has become a beloved spot
for locals to gather, swim, and enjoy the natural wonder.
In the 1920s, the water flow in the spring was strong enough
to shoot water six feet high in the air.
But over the last couple decades,
the spring's flow has slowed, and even stopped twice,
in 2000, and again in 2008.
This has allowed experienced divers to explore Jacob's Well
and the untouched cave system below.
(water splashes)
What they found was one of the longest
and most dangerous underwater cave systems in the country.
From the moment you enter the water,
it's clear that the pool is different.
Jacob's Well and its complicated cave system
has claimed the lives of at least 10 divers over the years
who were trapped down in the dark water.
The first two chambers are fairly safe
for experienced divers on their way down.
The first is an open drop for about 25 feet.
The sunlight still shines through the water,
which makes it easy to see what you're doing.
The second chamber continues down about 30 to 60 feet.
This is where things get tricky and dangerous.
Inside the second chamber is a false chimney
carved into one of the walls.
To a diver heading back to the surface,
it might look like a passageway.
But this trap has killed at least one diver in the past.
(static buzzes)
The third chamber continues downward like a funnel,
and cold water getting darker and deeper
the diver descends, ending at 75 feet down.
The opening to the fourth chamber is so narrow
that some divers even have to remove their oxygen tanks
to fit through.
The floor of this small room is made of silt and gravel,
and that can easily stir up,
making it hard for divers to tell up from down,
and which way is out.
The fifth chamber is extremely narrow limestone tube
that continues along at almost 100 feet below the surface.
The passage is so tight
that a diver's tank might scrape against the ceiling.
At that depth, strong flows from the spring push divers
back up, making it a struggle to swim down
to the deepest depths.
Most experts believe there are more chambers to discover,
descending even deeper into the earth.
But despite the deaths and clear-cut hazards,
thrill-seeking divers refuse to stay away,
drawn to the dark mysteries of the strange underwater caves.
Locals have gone as far as installing underwater signs
to try and warn anyone down there of the risks.
One man took it a step farther,
installing a large iron gate over the opening
of one of the most deadly caves.
But just a short time later, the gate was found removed,
tossed aside, with a handwritten note attached,
reading "You can't keep us out!"
So it seems clear that no amount of peril or warning
will keep mystery seekers from searching the deepest,
darkest crevices of the planet,
looking for anything they might find
that's out of the ordinary.
(upbeat music)