One dead body was also recovered from the tourist boat, which capsized off the coast of Alanya in the coastal Antalya province, said the coast guard command.
Speaking to reporters, Alanya Mayor Adem Murat Yucel said the casualty, a 37-year-old foreign national, had been caught in a narrow area of the boat and was unable to get free.
The tour boat sank for unknown reasons some 50-100 meters (164-328 feet) from the Alanya Castle Phosphorus Cave, also known as the Blue Grotto.
Ambulances were waiting at the scene of the accident.