A quad bike rider is critically ill after he fell 25ft (7.5 metres) from a sea wall in North East Lincolnshire.
The 25-year-old man, from Grimsby, was riding along the wall at Stallingborough when he fell on to the shoreline below.
He was taken by RAF helicopter to Hull Royal Infirmary, where he is receiving treatment for head injuries and is said to be in a critical condition.
The coastguard has warned people to be careful when moving along sea walls.
The man was with a friend, who was riding another quad bike, at the time of the incident.
Humberside Police has appealed for anyone who saw the two men in the Grimsby or Cleethorpes area or anyone who witnessed the incident to come forward.
The coastguard said it was asked to provide assistance by the ambulance service after paramedics responded to a 999 call and realised they could not reach the man.
Coastguard watch manager Mike Green said: "We are often asked to provide assistance to the ambulance service but rarely to rescue someone who has driven a heavy vehicle off a sea wall.
"I think that it goes without saying that people need to be very careful when moving along sea walls, cliffs or promenades that have large drops down to the beach. The unexpected can always happen."