A giant pumice raft was discovered by an Australian couple sailing near Fiji.
Michael Hoult and Larissa Brill, who were on board, were sailing their catamaran near Vava'u when they sailed through the rocks.
The pumice is formed of different stones, some the size of a basketball, and is roughly the same size as Manhattan in New York.
Another sailor, Shannon Lenz, posted incredible footage sailing through the rock raft.
"We sailed through a pumice field for 6–8 hours, much of the time there was no visible water,” Lenz wrote.
“It was like ploughing through a field. We figured the pumice was at least 6 inches thick.”
The pumice raft, which has been caught on satellite images by Nasa, is expected to drift towards Australia.
There is hope that the raft could float towards the Great Barrier Reef and bring a new lease of life to the coral.