- [Narrator] The world's oceans are under siege.

Marine life is dying at alarming rates

due to accelerating pollution, overfishing,

and climate change.

- People keep saying, “We're at a tipping point."

Some people say, "We're beyond a tipping point."

- [Narrator] But six miles off the shores of Key Largo

and 60 feet deep sits Aquarius,

the world's only underwater research laboratory.

- There is no other place where people live underwater

and work underwater for extended periods of time.

- [Narrator] The diver-scientists who work here

are called aquanauts,

and they come from all over the world to spend weeks

at Florida International University's Underwater Lab,

conducting cutting-edge research on oceanic health.

This elite group faces danger in the elements

for the sake of the planet in a race against time.

- The research at Aquarius,

it's being conducted at a critical time.

Aquarius, Aquarius Reef Base.

(garbled radio transmission)

That's a roger.

We got the main lock on.

Aquarius is the last undersea research laboratory

dedicated to science and education in the world today.

- There is no other underwater habitat

doing what we do how we do it.

- [Aquanaut] It allows researchers to live

at their study site.

They can do incredibly long working dives,

dives which couldn't be done from the surface.

(water splashing)

- When you're diving from the surface,

the deeper you go the less time you have.

When you live underwater,

the habitat actually becomes your surface.

When you dive from the habitat, which is about 50 feet,

and you dive to 90 feet,

you're not really diving to 90 feet;

you're really diving to 40 feet from the surface.

So, now what you've done is you've extended

that time period that you can actually spend at 90 feet.

That's where it really separates

from the traditional research or work that's done

from vessels on the surface of the water.

That makes a big difference.

- [Thomas] Marine ecologists use it as a base of operation.

Others wanna use it

for extreme-environment mission operations.

We do a number of projects with NASA,

and they say that Aquarius is very similar

to what astronauts experience in space.

- Everybody, when they're five years old,

wants to be an astronaut or a marine biologist.

I never grew out of it.

Living and doing science underwater

is the coolest thing I could possibly imagine.

- What does it take to become an aquanaut?

We look at people who have

considerable experience underwater.

Diving has to be second nature.

It's not uncommon for people

not to finish aquanaut training.

They start to understand that, maybe psychologically,

"I'm not prepared to be in a confined environment

"with five other people for 10 days."

- That's the typical length of missions,

but we have done longer ones.

We've done 16-day; we've done 18-day.

The longest one to date have been 31 days long.

- [Thomas] We've saturated 392 scientists now.

- Both you guys got your mask, fins, BC, depth gauge,

pressure gauge, computer.

- [Aquanaut] Check.

- I can honestly tell you from the bottom of my heart

that I enjoy waking up in the morning, and then coming to work.

Yeah, I enjoy my job, a lot.

- It's not an easy job, keeping Aquarius going,

constantly fighting weather, constantly fighting corrosion,

but everyday we wake up and say: "All right,

"we've gotta do something today because

"what's happening with the oceans isn't stopping."

(funky electronic synthesizer music)