Fabien Cousteau, the grandson of legendary French oceanographer Jacques Cousteau, emerged from the deep Wednesday after 31 days in an undersea lab off the Florida Keys.

The 46-year-old Cousteau -- whose efforts bested a 30-day mark set by his grandfather a half-century ago -- and his "Mission 31" returned to Islamorada at about 10:00 am (1400 GMT).

His team cheered and greeted him with hugs at the coastal Florida International University facility that operates the bus-sized Aquarius Reef Base undersea research laboratory, the only one of its kind and located 20 meters (65 feet) below the surface.

"This has been a monumental success on multiple levels," Cousteau told a press conference.

Cousteau said he was "elated" about the quality of the work, but "exhausted" from spending more than a month under water, where his team carried out a battery of experiments, some of it streamed live online.

"We achieved more than we imagined possible," he told AFP. "The most important thing was reaching the maximum amount of people for 31 days on multiple platforms."

The goal of the mission launched on June 1 was to observe marine life, the effects of pollution on coral and how long-term underwater stays affect people.

Scientists took daily diving trips outside the lab to carry out experiments also focused on climate change and ocean acidification.

Cousteau allowed ocean enthusiasts to follow his mission in real time via the Internet -- a live feed at www.mission-31.com.

He conducted educational seminars with schools, museums and aquariums from the undersea lab, where conditions were extremely humid.

Cousteau told AFP before the mission that he was seeking to honor the legacy of his grandfather, who spent 30 days under the Red Sea in the early 1960s -- one of his many ocean voyages.

The elder Cousteau used footage from that experience in his Oscar-winning documentary "World Without Sun," one of his many films. Jacques Cousteau died in 1997.

"I think he would have loved to be able to talk to so many people," Fabien Cousteau said.

He said the mission marked the "first time a Cousteau expedition was able to share the daily lives" of the explorers, calling the experience "a little strange and a lot of fun."

Cousteau said the team members lived together in close quarters without incident, though they all missed their family and friends.

- 'Bittersweet moment' -

Cousteau and his team had to undergo 16 hours of decompression before returning to the surface -- a lengthy process during which they watched "World Without Sun."

"It was a bittersweet moment," Cousteau said of returning to normal life, though he admitted it was nice to breathe fresh air and feel the ground under his feet.

"Leaving such a special place was a little bit of a hard time," he added.

Cousteau noted it was not all work and no play: at one point, he tried -- unsuccessfully -- to play football underwater, in a nod to the ongoing World Cup.

He said the team would now focus on combing through all of the images taken, for an eventual documentary, and the data from the various experiments.

The scientist did not rule out a "Mission 32" but admitted it would be difficult for him to lead it, given the enormous commitment involved.

For the oceanographer, who spent much time with his grandfather aboard the Calypso, staying underwater for 31 days was a dream come true.

"It has been an absolutely amazing experience on so many levels," he said with a smile.