The second in line to the British throne, who is a Royal Air Force helicopter and known professionally as Flight Lt. William Wales, was aboard an aircraft which rescued two crew members early on Sunday, after their vessel suffered a cracked hull in gale force winds off the coast of north Wales.
Britain's ministry of defense said William had been co-pilot of the helicopter, which carried two people back to his base RAF Valley, on the Welsh island of Anglesey.
Authorities said five people remain missing after the Swanland cargo ship, which had eight people on board and was carrying thousands of tons of limestone, sent a mayday call.
Holyhead Coastguard said one body had been recovered from the sea, but that the fate of the other crew members was not yet known.
"We know that at least some of them are wearing immersion suits and have strobe lighting with them, however sea conditions are challenging at best," said Jim Green, a coastguard spokesman.
Rescue helicopters from RAF Valley and from Dublin coastguard base in Ireland were initially sent to the scene, about 20 miles (32 kilometers) northwest of the Llyn peninsula in north Wales.
Helicopters from RAF Chivenor, in southwest England, and the Irish Coastguard are continuing to search for the missing crew, along with boats from the Royal National Lifeboat Institution.
"Two RNLI lifeboats, along with four search and rescue helicopters and two other commercial boats, are searching for the remaining six crew," the RNLI said in a statement.
Gale-force winds battered the Irish Sea during Sunday and the coastguard said it is believed the poor condition could have caused the incident.