NASA's Training For Deep Space Means Living In The Deep Sea First

Astronauts and other scientists are calling the Atlantic Ocean home for the next few weeks.

The NASA Extreme Environment Mission Operations — also known as NEEMO-21 — began July 21 and will last 16 days.

The underwater mission allows crews to prepare for deep-space missions by conducting research, testing new tools and even doing simulated spacewalks.

Aquanauts are stationed on Florida International University's Aquarius Reef Base. At 62 feet below the ocean's surface, it's the world's only undersea research laboratory.

Astronauts participating in the 21st mission are from the U.S., Ireland, Germany and South Africa.

SEE MORE: Five Years Later, Juno Finally Got The First In-Orbit Photo Of Jupiter

Some will remain on the mission for 16 days, while others will rotate out halfway through.

This video includes clips from NASA Johnson and images from Facebook / NASA NEEMO, Facebook / Aquarius Reef Base and NASA / Karl Shreeves.