A SpaceX spaceship splashed down in the Gulf of Mexico on Tuesday carrying precious cargo: two astronauts who have been stuck in space for nine months.

Butch Wilmore and Suni Williams were the first astronauts to fly aboard Boeing's Starliner spaceship, which carried them to the International Space Station in June.

Their mission was originally set to be about eight days, since it was just a demonstration to show the spaceship could fly humans.

That didn't work out. The Starliner's engines glitched as it approached the ISS. After weeks of review, NASA decided to send Starliner back to Earth empty and wait to bring Wilmore and Williams back on a SpaceX vehicle.

Now, finally, they've returned home.

Williams and Wilmore boarded the SpaceX Crew Dragon early Tuesday morning alongside their two new crewmates: NASA astronaut Nick Hague and Russian cosmonaut Aleksandr Gorbunov.

With the help of other astronauts on the ISS, they closed the spaceship's hatch, then sat suited up and buckled in as the Crew Dragon slowly backed away from the station.

They cruised in orbit for about 12 hours, then returned to their seats and buckled in for the series of spacecraft maneuvers that would bring them back to Earth.

Shortly after 5 p.m. ET, the Dragon fired its engines for about seven minutes to push itself out of orbit, onto a trajectory to fall toward the waters off the coast of Florida.

About 30 minutes later, the spaceship began plowing through the thick of the atmosphere, its belly of heat-resistant panels acting as a heat shield to protect it from the superheated plasma gathering around it.

Soon the spaceship deployed a set of parachutes, jerking it into a slowed fall. It drifted into the Gulf of Mexico at about 5:57 p.m. ET.

The spaceship was "full of grins ear to ear," Hague told mission commanders from inside the capsule.

SpaceX crews pulled the capsule from the water, opened its hatch, and helped the astronauts climb out.

Watch the whole journey in NASA's livestream, below.

Williams and Wilmore have both said that they enjoy being in space and were prepared for the possibility that their deployment would be extended, but they also said that they missed their families and friends.

"Every day is interesting because we're up in space and it's a lot of fun," Williams said in a press conference from the ISS two weeks before their return.

"The hardest part is having the folks on the ground have to not know exactly when we're coming back,"Williams added.

They quickly became known as the "stranded" astronauts, though NASA officials disagreed with that terminology.

SpaceX has already successfully flown nine astronaut crews to space and back aboard its Crew Dragon spaceship, as well as five private crewed missions.