The grandson of famed French oceanographer Jacques Cousteau began a potentially record-breaking 31-day underwater stint off the US coast Sunday, with his mission declaring "splashdown!!!" as the expedition got underway.
Fabien Cousteau, 46, and crew dove off the state of Florida's Key Largo coast, where they will conduct experiments in a bus-sized lab named Aquarius some 65 feet (20 meters) underwater and work with documentary filmmakers.
Cousteau and crew could be seen via live images transmitted online only minutes after they began their descent, when they declared "mission 31 splashdown!!!" just before noon (1600 GMT) on Twitter.
Cousteau is also hoping to beat a record set by his grandfather a half century ago when the elder Cousteau -- who died in 1997 -- spent 30 days underwater in the Red Sea.
On the eve of his dive, Fabien Cousteau told AFP that if he makes it to his target date, he will break his grandfather's record to "honor" his legacy and "his aquanauts and all the previous aquanauts who have done such fantastic work."
Mission 31, named for the number of days the crew plans to remain submerged, includes scientists, engineers and camera people.
Three of the researchers, led by Cousteau, will stay put under water until July 2, observing sea life, the effects of pollution on coral and of long-term underwater stays on people.
Every day, they will be able to dive for about 12 hours until 10:00 pm, when they will rest for eight hours.
The explorers, who can be followed live at www.mission-31.com, could be seen via an external camera an hour into the mission already swimming around Aquarius.
"It's the first time that a Cousteau expedition has ever been able to invite the world in real time" thanks to the Internet, the explorer said, noting that teammates would be able to speak to students during the effort.