On January 3, 2015, about 1015 eastern standard time (EST), a Cessna P206, N2534X, was force landed in a lagoon following a total loss of engine power during an approach to Key West International Airport (EYW), Key West, Florida. The airline transport pilot and three passengers received minor injuries and two passengers were not injured. The airplane was substantially damaged. The airplane was operated by Exec Air Inc. under the provisions of 14 Code of Federal Regulations Part 91. Day, visual meteorological conditions prevailed, and no flight plan was filed. The flight originated at Naples, Florida (APF) about 0920. The pilot reported the following. About 300 feet above the ground, on final approach to runway 9, the engine "quit suddenly with no surging or other warning signs." He selected the auxiliary fuel pump to the high position and switched fuel tanks. The engine "came back to life momentarily and then quit again." Unable to make the runway, the airplane landed short in a lagoon, about one quarter mile from the runway. The airplane came to rest in about 3 feet of salt water. The pilot reported that he departed APF with about 78 gallons of fuel on board. An inspector with the Federal Aviation Administration responded to the accident site and examined the wreckage. The right wing exhibited structural damage from impact forces. The fuel selector was in the "off" position; however, he reported that the selector handle was moved to off from the "right tank" position by recovery personnel. The wing tanks were also de-fueled prior to his arrival. About 15 gallons of fuel were recovered from the left tank and about 40 gallons of fuel were recovered from the right tank. The nose gear was crushed upward, into the underside of the engine. There was no fuel or oil observed on the exterior surfaces of the airplane. A fueling record was recovered that indicated 42.2 gallons of fuel was purchased at APF prior to the flight. Fuel was observed in the lines between the electric boost pump and the engine-driven fuel pump, in the line from the engine-driven pump to the fuel metering valve, and there was fuel in the line entering the fuel manifold valve and inside the valve. The engine-driven fuel pump appeared normal and the drive shaft was intact. The top six spark plugs were removed and were normal in appearance. The engine was turned by hand; internal continuity was established and compression and suction was confirmed an all six cylinders. The magnetos were tuned by hand; the impulse couplings appeared to operate normally. No spark was observed on the ignition leads when the magnetos were turned. The magnetos and ignition harnesses were retained by the FAA inspector for additional examination and testing. On April 9, 2015, the magnetos, ignition harnesses, and engine driven fuel pump were examined at the Continental Motors facility at Mobile, Alabama under the direction of the NTSB. The fuel pump (part # 638154-1; serial # 1752) did not exhibit external damage. The spline on the fuel pump was intact and the unit rotated when actuated by hand. The fuel pump was installed on a test stand and ran at rpms between 700 and 3,200 for several minutes. The unit functioned as designed and the recorded pressure was high. The left magneto (Slick model # 6210; serial # 90080047) did not exhibit external damage. The left magneto was installed on a test bench and ran at different rpms for several minutes. A blue spark was observed on each lead at varying rpms. The right magneto (Slick model # 6210; serial #91040206) did not exhibit external damage. The right magneto was installed on a test bench and ran at different rpms for several minutes. A blue spark was observed on each lead at varying rpms. Two passengers reported to an FAA inspector that the airplane was "chartered" by a third passenger for the round trip flight to EYW. A credit card receipt for $1,180.80 was provided to investigators, on the third passenger's credit card and charged by the operator, Exec Air. Exec Air holds an FAA Airline Certificate for On Demand Airplane operations. The certificate only has 1 approved aircraft, a Cessna 182. The Cessna 206 used in the accident flight is not approved on the certificate. The owner of Exec Air reported after the accident that the charge to the passenger's credit card was for anticipated expenses incurred during the personal flight. The FAA is pursuing certificate action against the operator and pilot for conducting an unauthorized charter flight. At the time of this writing, that action was still pending.