Volunteers from RNLI launched to reports of two paddleboarders in trouble in Poole Harbour.
One person made it ashore, while the other was found clinging to a mooring post near Evening Hill on Saturday.
The casualty, who was very cold, was rescued by the Poole lifeboat crew and taken to Salterns Marina for treatment before being passed to ambulance crews.
Crews say the weather changed quickly, with strong winds and rain catching the paddleboarders off guard.
They are reminding people to wear buoyancy aids and always carry a way to call for help.