Fire-Rescue was called to the boating accident near the Nixon Beach Sandbar around 10:45 p.m., said Lt. Pete Sanchez, Miami Fire-Rescue spokesman.
Two vessels had collided and there were 11 people in the water. Five people had been on one boat and seven on the other, Sanchez said.
Sanchez said two people in critical condition were transported immediately: An adult male was airlifted and a 15-year-old was transported to a local trauma center.
Nine others were rescued from the water — six were taken to the hospital with minor injuries and two with serious injuries, according to Sanchez. One person refused transport.
One person remained missing Saturday morning following two and half hours of search and rescue efforts involving a helicopter and divers, Sanchez said.
The search has now moved to a recovery effort, with the US Coast Guard leading the mission, Sanchez said.
Miami-Dade Fire Rescue, City of Miami Fire Rescue, Key Biscayne Fire Rescue, and the US Coast Guard responded to the collision, according to Sanchez. The Florida Fish and Wildlife Conservation Commission is investigating.