On September 30, 1996, about 1215 eastern daylight time, a Bell 206B III helicopter, N2113Z, registered to the United States Department of the Interior, operating as a Title 14 CFR Part 91, public-use flight, crashed in the vicinity of Flamingo, Florida. Visual meteorological conditions prevailed and a company flight plan was filed. The helicopter was substantially damaged. The airline transport pilot and one passenger were not injured. The flight originated at the Everglades National Park, about 0700. This flight was on a mission for the United States Geological Survey, taking water samples in the Florida everglades. According to the pilot's statement: "While taking off from a level site, covered with about 4-6 inches of water and moderately covered with mangrove vegetation, the wire strike protection guide made contact with a mangrove plant branch. This caused the nose to pitch down while the helicopter was trying to transition to forward flight. The helicopter also rolled to the right causing the rotor blade to strike the ground." The National Park Service (NPS) was providing flight following for the flight, and the pilot was to report every 15 minutes. The NPS had been provided with the starting geographic coordinates, and subsequent coordinates before starting each leg. The crew had indicated to NPS flight following personnel that the flight would be west to east, collecting data at 400 meter intervals. In addition, NPS was alerted when and where the flight would land for fuel. The flight had 7 minutes remaining before the next report was to be made, when the accident occurred. What was not known to the pilot was, the NPS dispatcher had closed after the last report, and the pilot was not notified of the situation. The helicopter's emergency transmitter locator (ELT) did not operate after the crash, and no one was aware of the accident, until a ground crew member became concerned when he had not heard from the flight for about 5 hours. The ground crew member checked with NPS personnel, and expressed his concern. The occupants stayed with the helicopter until about 1845, when they were rescued by a Coast Guard helicopter. Examination and a functional test on the ELT from this helicopter revealed that the "ON-OFF-ARM" switch was not working. Disassembly of the ELT did not expose the interior of the switch, and there was no determination made on why the switch malfunctioned.