06x09 - Searching for the Rare Blind Crayfish + Odd Shark Behavior + Exquisite Leafy Seadragon

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- [Narrator] Today on "Blue World,"

Jonathan searches a Florida cave

for a rare blind crayfish.

Then he takes his whole
family to Australia

on a search for the world's
most magnificent seahorse.

But first, the science
of hammerhead sharks.

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Meet Jonathan Bird,

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one of the world's top underwater
nature cinematographers,

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traveling the world on assignment

for all the major networks.

He is an Emmy Award-winning authority

on the underwater world.

In fresh water or salt,
reefs, wrecks or caves,

Jonathan documents the
world beneath the wave.

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Welcome to the "Blue World."

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- [Jonathan] The underwater
world is full of mysteries

to be solved.

One such mystery involves
the great hammerhead shark.

Divers rarely see great hammerheads.

They're known for being shy loners,

unwilling to approach people.

But a few years ago,

divers began visiting a
place near Bimini Island

in the Bahamas where great hammerheads

have been caught by fishermen for years.

They found a special
place with lots of sharks.

Over time, the sharks got used to divers

and started coming in close for a snack,

giving people an intimate look

at the great hammerhead shark.

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I've been to Bimini several times

and I'm always amazed by how
huge great hammerheads are.

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Not only does the head
reach a meter or more wide,

but the tall dorsal fin is a
striking feature of this unique

and majestic shark.

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And in spite of the aggressive appearance,

great hammerheads almost
never attack people.

They much prefer to eat
stingrays in the sand,

but diving with great
hammerheads has allowed divers

to notice something unusual.

The shark often swims tilted
to the side at an angle.

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I also noticed behavior in
the Ocean Voyager exhibit

at the Georgia Aquarium.

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My friend Andy Casagrande,

one of discovery channel's

primary Shark Week cinematographers

wanted to help investigate the mystery

of the leaning hammerhead.

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He attached a GoPro camera
to the huge dorsal fin

of a great hammerhead

to film the shark for an
extended period of time.

His amazing footage shed
light on the behavior

of these sharks, and it has
to do with their anatomy.

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The hammerhead shark never stops swimming,

but contrary to popular
belief, many sharks do.

Most species of sharks
like the lemon shark,

can rest on the bottom

and move water over their
gills by simply gulping.

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Biologists call it buckle pumping.

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A few species of sharks
like the whale shark

and the white shark, are known
as obligate ram ventilators.

They can only breathe by
ramming oxygenated water

into their gills through
their mouths as they swim.

If they stop swimming, they'll suffocate.

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The great hammerhead is
an obligate ram ventilator

and has to keep swimming all the time.

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Sharks such as the blue shark

keep swimming all the time too,

but for a totally different reason,

because sharks sink if they stop swimming.

Fish including sharks are
heavier than water, so they sink.

Bony fish have an organ
called a swim bladder

that they use to adjust their buoyancy.

By adjusting how much gas
is in its swim bladder,

a fish can keep itself perfectly neutral,

so it doesn't sink or float.

Since sharks have no swim bladder,

they sink to the bottom
when they stop swimming.

But some sharks like the blue
shark live in the open ocean

where the bottom is
thousands of feet below,

where it's dark and cold.

They can't rest on the bottom.

So they've adapted to this environment

by developing very large pectoral fins

to act as airplane wings.

As the shark cruises through the water,

the fins provide lift
to keep the shark aloft

and prevent it from sinking
into the dark cold abyss.

The bigger the pectoral fins,
the more lift they provide,

and the slower the shark
can swim without sinking,

which saves energy.

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The great hammerhead, on the other hand,

has small pectoral fins

and a big head called a cephalic foil.

The cephalic foil seems to
accomplish several things

for the shark, including expanded vision,

a larger surface area
for electro receptors

and additional front end
lift like a mini wing,

but it also has mass

and scientists think this mass

combined with small pectoral fins

is the reason that hammerheads

are so much more maneuverable

than other similarly sized sharks.

But while those small pectoral fins

help the shark turn quickly to catch prey,

they have a disadvantage, not much lift.

And this is where the
tilted swimming comes in.

Andy Casagrande's dorsal fin footage

showed that when great
hammer heads are on the move,

they're almost always
swimming at a tilted angle

of more than 45 degrees.

In 2015, Nicholas Payne, Gil Iosilevskii,

and five other researchers got together

to investigate this strange behavior.

They put sensors on
great hammerhead sharks

to measure the roll angles.

Then they used wind tunnel
tests to model the effect

and figured out what the sharks are doing.

The sharks roll on their sides

to use that huge dorsal fin as a wing

and provide lift while swimming distances.

It allows the shark to generate more lift,

which means it can swim a bit slower

without sinking and save energy.

In fact, swimming tilted to the side

saves the shark about 8% swimming effort.

So when the shark needs to go somewhere,

it tilts to the side and saves energy.

But when it needs to hunt,

it swims straight up and down

to take advantage of the
increased maneuverability.

The giant dorsal fin serves two purposes,

a keel when upright
and a wing when tilted.

At this point, no other shark is known

to use this technique,

and it explains a mysterious habit

that divers observed in
great hammerhead sharks.

Sometimes just being in the ocean

creates new understanding of
the life that lives there.

As divers, our time in
the ocean is fleeting,

lasting just an hour or so per dive,

but it affords us the
opportunity to catch a glimpse

of the lives of the
animals that live there.

This is one of the things
that keeps me coming back

over and over for my short
glimpses into the blue world.

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- [Narrator] Coming up,

Jonathan explores a Florida cave

in search of a rare cave crayfish.

- [Jonathan] It's a beautiful
morning on the Suwannee River.

I'm back in Florida to
explore some more of the caves

that have made this part
of the world famous.

Our first stop is Amigos Dive Shop,

where my good friend Wayne Kinard

has our tanks full and ready.

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We're on an expedition today,

looking for a blind cave crayfish,

which is a little albino
crayfish that lives in the caves.

It's very rare, but the cool thing is,

it lives to be 200 years old.

It's only a half hour drive from the shop

to Little River Springs.

This picture perfect spring
produces 55 million gallons

of crystal clear water every day,

and it's home to the
elusive cave crayfish.

This is my favorite part of of diving,

is when you get to carry your stuff.

We bring our tanks down to the water.

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Then it's time to suit
up for an adventure.

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Now how does this thing go together?

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Finally, Todd, Zach and I
are ready to begin our dive.

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I am really excited

because I've never dove this cave before,

but Zach and Todd have done it many times.

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At the entrance to the cave,

Todd ties his reel to a steel pin,

specifically designed for cave divers.

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This line is extremely
important for cave divers

as it points the way out of the cave.

A few hundred feet inside the cave,

Todd ties his line off to
the permanent guideline

that we will follow.

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Soon we leave the cavern zone

and head into a place
of perpetual darkness.

Since Zach is an expert on
this cave, he leads the way.

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The walls of the cave
show scratches from divers

struggling forward in
the high flow conditions.

We're lucky that the flow
is not too strong today.

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While Florida caves are
not ornately decorated

like caves in some other places,

the erosion of the limestone
creates an alien landscape

full of interconnecting
passages to explore.

You never know what's
around the next corner.

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We're having fun filming each other

as we swim further into the cave,

keeping an eye out for the crayfish.

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Finally, Todd spots a blind cave crayfish.

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It looks like a miniature lobster,

but since it lives its
whole life in darkness,

this crayfish has lost not only its sight,

but its pigment, so it's a ghostly color.

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Mission accomplished.

With the crayfish filmed

and having reached one
third of our air supply,

we turn and begin our
trip back to the entrance.

The way back is much easier

because we just go with the flow.

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Back in the cavern zone,

Todd removes his reel
from the permanent line

and spools it back up as we ascend.

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Up in the spring,

we spend a little time
filming the sunfish.

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Then I spot a really
cool freshwater flounder,

also known locally as a hogchoker.

Even in a tiny pool like this,

there are cool things to find.

We surface safely an
hour after we started.

That was awesome.

Caves may seem devoid of life,

but the cave crayfish

is a perfect example of how life can adapt

to virtually any environment
in the blue world.

- [Narrator] Coming up,

the bird family heads to Australia

in search of the world's
most exotic seahorse,

the leafy seadragon.

- [Jonathan] I love seahorses,

and I've filmed many different
species all over the world.

I've always wanted to
see a leafy seadragon,

which is almost certainly the rarest,

most spectacular seahorse in the world.

They're only found in one place,

the waters of Southern Australia.

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It's summer vacation,

and the whole family is joining me

on a "Blue World" expedition
to South Australia.

The kids have never been
on a flight this long.

We're traveling to the
other side of the world

from Boston all the way to Adelaide

with a stop in Dubai.

It's two 12 hour flights back to back.

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Well, it took 30 hours,

but we made it to
Adelaide, South Australia.

Sleeping on a plane is difficult,

so we're totally exhausted,

but we still have to load our rental van

and drive down to our
rental house in Rapid Bay.

Rapid Bay is a beautiful place

located a hundred kilometers
south of Adelaide.

We rented a house right on the ocean.

It's windy and not that warm.

It may be summer at home,

but here in the southern
hemisphere it's winter.

There's not much between
Rapid Bay and Antarctica,

except ocean.

The next morning we make
a run up to Adelaide

for scuba tanks.

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Then it's over to the dive
site, the Rapid Bay jetty.

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The roads are a blast,
even if I am in a minivan,

but I have to remember
to drive on the left.

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Well, I finally made it to the jetty

here in Rapid Bay in South Australia,

one of the best places in the world

to find one of the rarest
seahorses in the world,

the leafy seadragon.

The jetty in Rapid Bay
was originally built

for loading limestone
from the local quarry

onto cargo ships.

The quarry up on the
hillside is still here,

but no longer used.

The original jetty fell into disrepair,

but it was so popular with
the locals for fishing

that they spent $3
million building a new one

just for recreation.

It's popular with fishermen and divers.

We meet up with Daniel Kinasz,
a local dive instructor.

We take a quick walk down the
jetty while Daniel explains

the dive to me and Christine.

Then it's time for everyone to suit up.

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Christine and I are
putting on our dry suits.

Dry suits are kind of a pain,

but it beats being cold.

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The kids unfortunately
don't have dry suits yet,

so they'll have to dive in wetsuits.

But hey, their kids, they could take it.

The water's only 55 degrees Fahrenheit,

that's 13 degrees Celsius, chilly.

- [Diver] How long this is going.

- [Jonathan] It's time for
a long walk down the jetty,

or should I say a long
walk off a short pier.

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Fortunately, when they built the jetty,

they kept divers in mind.

So there's a nice staircase
right into the water.

The wind is howling and the
water is rough, but in we go.

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As we sink down,

I'm a little disappointed
by the visibility.

We knew it would be cold,

but we didn't count on a storm
churning up the sediment.

I can barely see Daniel ahead of me

as we begin our search
for leafy seadragons.

We're hunting in the seaweed

because that's where their
camouflage allows them

to hide the best.

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After what seems like forever,

we finally find one.

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In South Australia,

we found a leafy seadragon
in the murky water.

This master of camouflage looks exactly

like a drifting piece of seaweed

within the seaweed garden
on the ocean floor.

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Obviously, this is not an
animal designed for speed.

No seahorses are fast,

but this one is positively sluggish

with all those leafy projections.

But who needs to be fast
when you can blend in.

Predators just don't
see the leafy seadragon.

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This seadragon does use
whatever speed it has

to try to escape the
glare of my bright lights.

But once it figures out that
I'm not going to herd it,

the seadragon relaxes a little bit

and allows me to get in for some closeups.

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I don't even notice the cold water

when I'm filming something
awesome like this.

Once we know how to find
them, they're easier to spot.

Elise finds a pair of smaller ones.

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These conditions can't be easy
for the little seadragons.

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With the kids in wetsuits,
they get cold fairly soon,

so we head back out of the water.

The kids are cold, but excited.

- It's cold.

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- [Jonathan] We hoof our
gear back to the van.

Short diving is a lot of work.

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Now for our least favorite part.

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We came a long way for this little fish,

but it was worth it.

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I've waited 20 years to
see a leafy seadragon.

It's one of the weirdest,

most camouflaged animals I've ever seen.

A true wonder of the blue world.

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