Police described the incident in the Isle of Skye, which triggered a multi-agency emergency response, as an “unfortunate accident”.
The 53-year-old fell from Broadford Pier shortly after 4pm on Thursday.
Police, coastguard, ambulance and fire teams were sent to the scene and the man was recovered from the water.
He was airlifted to Queen Elizabeth University Hospital in Glasgow for treatment.
Portree-based Sergeant David Canning said: “Our thoughts at this time are very much with the family and friends of this male who has been involved in an unfortunate accident.
“I would also extend our thanks to the public for their quick thinking in assisting to recover the male and providing medical assistance.
“Our enquiries are on-going to establish the full circumstances and I would ask anyone with information who has not yet spoken to an officer to get in touch.”