A British man is thought to have drowned after going overboard on a ferry from Belfast to Liverpool on Saturday morning.
The man, aged 35 and from Runcorn in Cheshire, was travelling home on the Lagan Viking with his girlfriend after a short stay in Belfast, police said.
A major air and sea search was launched after he was seen going overboard shortly after 2am. The alarm was raised by the crew, who threw a marker buoy into the water and turned their vessel to begin the search.
Most passengers were asleep at the time and were unaware of the incident until after the vessel had broken off from the search and resumed its journey. Liverpool coast guard co-ordinated the search in an area 10 miles south of the Isle of Man.
A lifeboat from Port St Mary and a Royal Air Force helicopter from Anglesey were scrambled to the search area and a number of vessels, including the Lagan Viking's sister ship, the Mersey Viking and the survey ship Corystes, joined in the hunt.
The search was called off in the early afternoon and the Lagan Viking docked in Birkenhead at 8am.
Police spent several hours interviewing passengers, but they are not treating the case as suspicious, a spokesman for Merseyside Police said.