Police have recovered the body of a 19-year-old man from the Bannockburn inlet, the Kawarau arm of Lake Dunstan near Cromwell.
Police said emergency services were called after reports of two people in trouble while swimming in the river.
Earlier reports that the man was recovered from Lake Dunstan were incorrect.
The other person managed to get to the shore safely.
A police spokeswoman said emergency services were called to the incident just after 1pm on Saturday.
Cromwell chief fire officer Steve Shaw said two Cromwell vehicles were sent to the inlet at Bannockburn.
The Coastguard was called, but was turned away, he said.
Clyde chief fire officer Richard Davidson said a crew went out to the scene with a rescue boat, but the body was recovered before it arrived.
The area off Cairnmuir Road, Bannockburn, is popular for swimming.
