Schettino is on trial in the Tuscan city of Grosseto on multiple manslaughter charges and dereliction of duty in the Jan. 13, 2012, shipwreck that claimed 32 lives.
Stefano Iannelli said Schettino abandoned ship "just before the deck went under" during testimony Monday, ANSA reported.
Iannelli said he, Schettino and four other crew members went to a lifeboat when they didn't see any other passengers. He said he jumped into the boat and the captain followed.
"Just as the lifeboat took off, the ship fell on its side, and the deck where we had been went under water," Iannelli said.
During the trip to the Giglio Island shore, Iannelli said, "we recovered passengers in the water."