The 17-year-old boy died in Oak Creek, Wisconsin, which is south of Milwaukee, authorities said.
Crews responded to reports of three teens in distress Thursday night. Rescuers pulled two from the water, with one in critical condition.
The third teen was later found dead. Their identity was not immediately known.
SEE ALSO | Girls, 16 and 13, killed in WaveRunner crash on Lake Marie in Antioch identified by medical examiner
The victims were all believed to be related, officials said.
No further information was immediately available.
SEE ALSO | William Schulze, 75, of Elburn dies while crossing Iowa river during severe flooding