On August 13, 2010, at 2110 eastern daylight time, a Cessna 172R, N2435X, registered to Island City Flying Service, Inc., collided with the Atlantic Ocean while maneuvering in a traffic pattern at Key West International Airport (EYW), Key West, Florida. Night visual meteorological conditions prevailed, and no flight plan was filed. The airplane incurred substantial damage, and the certificated, non-instrument-rated private pilot sustained serious injuries. The local personal flight was conducted under the provisions of 14 Code of Federal Regulations Part 91. According to the first officer (FO) of an American Eagle flight that was inbound for landing at EYW, he and the captain overheard the accident pilot advise Navy Key West Approach Control that he would be conducting touch-and-go landings at EYW. After the subsequently switching to the EYE advisory frequency, the FO contacted the pilot over the radio. The pilot informed him that he had departed runway 9, that he was upwind at 200 feet, south bound, and that he would stay out of their way. The FO informed the pilot that they would be in front of him for landing. The pilot then stated that he was turning to the east and the FO observed the airplane on the traffic collision and avoidance system (TCAS). The FO also observed the landing light come on as the airplane started the turn. The landing light was reflecting off the water, and the FO asked the pilot if that was him. The pilot replied "yes" in a calm voice. About 10 seconds after the light came on, the landing light went out and the flight was no longer showing on TCAS. Further attempts by the FO to contact the pilot were unsuccessful. The pilot stated in an interview from a trauma center that he did not remember talking to the American Eagle flight or the collision with the Atlantic Ocean. He only remembered "bits and pieces" after the accident, and trying to remain afloat until he was rescued. The pilot did not report any mechanical malfunctions, and according to the owner of the airplane, the pilot related to him that "the engine did not quit." Review of the sun and moon data obtained from the U.S. Naval Observatory revealed that the moon's phase was "waxing crescent" with 18 percent of the disk illuminated. The FO, who flew both his own, as well as the accident airplane from EYW, wrote in a statement that there was very little moonlight and "a turn to the south with no light on the horizon can cause severe vertigo and disorientation." Federal Aviation Administration Advisory Circular 60-4A states, "The attitude of an aircraft is generally determined by reference to the natural horizon or other references on the surface. If neither horizon nor surface reference exists, the attitude of an aircraft must be determined by artificial means from the flight instruments. ...Spatial disorientation to a pilot means simply the inability to tell which way is up....Lack of natural horizon or surface reference is common on over water flights, at night, and especially at night in extremely sparsely populated areas, or in low visibility conditions". The wreckage was not recovered and search efforts were terminated by the insurance company. The pilot reported that his logbooks were in the airplane.