Kevin McGrath, 26, was reported missing from the Carnival Conquest cruise ship.
He was last seen by his brother in his cabin early Monday morning.
He was supposed to meet with family for breakfast before disembarking the ship, but he never arrived.
Carnival crew members, the U.S. Coast Guard, and the Miami-Dade Police Department searched the ship and the water for McGrath, but he was not found.
Surveillance systems and the U.S. Customs and Border Patrol did not find McGrath once passengers were disembarking the ship
Miami-Dade authorities also checked security cameras, none of which indicated that he may have gone overboard.
McGrath's whereabouts are still unknown.