Police said the man went ''down and under'' the bridge over the Clutha River at Allangrange Rd.
A police spokeswoman said a man fell from a jet ski into the river about 9.30pm.
Police and fire services were sent to the scene and rescued the man, who went ''down and under'' the bridge at Allangrange Rd.
A helicopter was sent but quickly stood down, the spokeswoman said.
The man rescued was ''cold and wet'' when seen by ambulance staff.
A St John spokesman said Balclutha ambulance staff found two patients when they arrived at the scene at 9.48pm.
There were no details on their age or genders.
One was in a serious condition and the other ''in a minor condition''.
They were both transported to Dunedin Hospital.
No further information was available.
