Abstract: A combined submersible vessel and unmanned aerial vehicle preferably includes a body structure, at least one wing structure, at least one vertical stabilizer structure, and at least one horizontal stabilizer structure. A propulsion system is coupled to the body structure and is configured to propel the flying submarine in both airborne flight and underwater operation. Preferably, the propulsion system includes a motor, a gearbox coupled to the motor and configured to receive power generated by the motor and provide variable output power, a drive shaft coupled to the gearbox and configured to transfer the variable output power provided by the gearbox, and a propeller coupled to the drive shaft and configured to accept power transferred to it from the drive shaft. The propeller is further configured to rotate and propel the flying submarine in both an airborne environment and in an underwater environment.