Английский словарь американских идиом - at sea(1)

{adv.} or {adj. phr.} 1. On an ocean voyage; on a journey by ship. * /They had first met at sea./ 2. Out on the ocean; away from land. * /By the second day the ship was well out at sea./ * /Charles had visited a ship in dock, but he had never been on a ship at sea./