Miami-Dade Fire Rescue also recovered a body from the water, the statement said.
A person involved in the collision notified the Coast Guard around 10:30 p.m. Friday, reporting 12 people in the water about a mile west of Key Biscayne, the statement said.
A survivor who was seriously injured was taken to Jackson Memorial Medical Center, the Coast Guard said.
Coast Guard crews transferred the remaining survivors to HCA Florida Mercy Hospital, the statement said.
“On behalf of the Coast Guard and our partner agencies, we wish to offer our deepest condolences to the families and friends who have lost loved ones,” said Lt. Cmdr. Benjamin Tuxhorn, Miami Coast Guard Sector Search and Rescue Mission Coordinator.
“The Coast Guard and our local partner agencies responded quickly and worked together comprehensively on this search and rescue case.”
The Florida Fish and Wildlife Conservation Commission is investigating the accident.