Emergency services launched a huge rescue mission in the area of the chain ferry crossing between Sandbanks and Studland on Tuesday morning, December 17.
Reports came in initially of two people in the water, but it was later determined that just the one man ended up in the sea.
Details of how he ended up in the water in the first place are not known by Dorset Police and have not been revealed by the Coastguard.
HM Coastguard sent up a search and rescue helicopter sent from the Solent area to carry out searches before it was known just the one man was in the water.
It was seen circling the perimeter of the harbour on the quay side.
Meanwhile, the chain ferry temporarily suspended its services while the emergency services carried out its jobs.
A spokesman for the Coastguard said: “At around 6.45am, HM Coastguard attended an incident at Sandbanks in Poole.
“Coastguard rescue teams from Swanage, Poole and Southbourne were called, alongside an HM Coastguard Rescue Helicopter and the RNLI Poole lifeboat.
“Dorset Police and South Western Ambulance Service also attended, and the search was stood down at around 8am.”
The spokesman said the Coastguard received a report relating to a welfare incident and that once it was established the one person had been rescued, the search was stood down.
He added the man had recovered himself to safety.
South Western Ambulance Service said they were called at 6.06am and sent an ambulance and an operations officer to the scene.
A spokeswoman added: “We conveyed one patient by land ambulance to Poole Hospital.”
Dorset Police said officers were called to a “concern for welfare of a man who had been in the water near to the ferry”.
A spokeswoman added: “The man was taken to receive treatment and the appropriate care by the ambulance service.
“Searches were carried out by HM Coastguard and the RNLI and following further enquiries, it was established that nobody else had entered the water.”
A spokeswoman for the chain ferry said: “We delayed the start to this morning’s service to assist the emergency services in dealing with an incident.
“The ferry service is now running normally. ”