Rescue crews were searching a stretch of coastline on Tuesday after a man was swept into the sea in gale-force winds.
The 41-year-old was reported to have been walking his dog in Blackpool with another man when both men ended up in the water shortly after midnight.
The second man was able to get to safety and raise the alarm.
A search was carried out overnight by RNLI and Coastguard crews from Blackpool and Lytham St Annes, assisted by the Lancashire Police helicopter and the search and rescue helicopter from RAF Valley on Anglesey.
A second search operation got under way just after first light today and remains ongoing.
Stuart Atkinson, watch manager at Crosby Coastguard station, said: "We received a call at 12.13am from
Lancashire Police reporting that a male was in the water near the South Pier at Blackpool.
"A second male had been in the water but managed to get to safety and raise the alarm.
"We believe, but it's not confirmed, that they were walking their dogs.
"A search was carried out by coastguard rescue units, the local RNLI lifeboats from Blackpool and Lytham St Annes and the police helicopter.
"The rescue helicopter from RAF Valley was also there providing lighting assistance for the search teams.
"The area was searched and unfortunately we didn't find the 41-year-old male at that time, but we are carrying out a second search at the present time.
"We do believe a life ring was thrown to him and a football. We have located the football but not the life ring."
Mr Atkinson said the search operation was hampered last night due to very strong, westerly gale-force winds.
"As you can imagine, westerly winds are aimed straight at the sea shore at Blackpool and it made it quite difficult for the lifeboat crews to search," he said.
The current search was focusing on an area of the Irish Sea around the South Pier and the Blackpool sea wall.