Police say a man was seriously injured this afternoon when struck by a 15 metre yacht near Motuhie Island in Auckland's Hauraki Gulf.
They said the man had jumped into the water, thinking the boat he was on was going to collide with the yacht.
He was pulled from the water - unconscious but breathing.
The Coastguard transported the man to an ambulance at Mechanics Bay.
No one else was harmed in the incident.