On July 21, 2004, approximately 0824 central daylight time, a Bell 206B single-engine turbine powered helicopter, N133RT, registered to and operated by Omni Energy Services of Carencro, Louisiana, was substantially damaged when it submerged under water after an autorotation following a loss of engine power while maneuvering near East Cameron 13, an offshore platform located in the Gulf of Mexico. The commercial pilot sustained minor injuries and his two passengers were not injured. Visual meteorological conditions prevailed, and a company flight plan was filed for the 14 Code of Federal Regulations Part 135 on-demand air taxi flight. The flight originated at 0740 from Vermillion 218, and was destined for the Air Logistics Heliport (LA53) near Grand Chenier, Louisiana. The operator reported in the Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2) that during cruise flight, the "engine lost power." The 21,440-hour pilot initiated an autorotation to the water from an altitude of approximately 500 feet. Subsequently, the helicopter touched down on the water, rolled inverted, and sank. The helicopter was equipped with emergency floats. In a written statement, the pilot stated that after performing a 180-degree autorotation, he armed the emergency floats, but did not trigger the floats to inflate. The pilot added that prior to touchdown, the helicopter "fell the last 12-15 feet," before landing on the water. The helicopter was recovered to the facilities of Omni Energy Services in Carencro, Louisiana, for further examination after being submerged in salt water for approximately three days. Examination of the helicopter, by representatives from Rolls Royce and Bell Helicopter was under the supervision of an Federal Aviation Administration (FAA) inspector. Examination of the engine revealed that the engine remained attached to its respective mounts. The compressor rotor would not rotate. The delivery and return oil lines on the engine between the accessory gearbox and compressor front support, gas producer turbine support, and power turbine support were secure and undamaged. The pneumatic lines between the compressor scroll, power turbine governor, and fuel control were secure and undamaged. The throttle linkage was securely connected to the fuel control arm. The fourth stage turbine wheel rotated freely in a counter-clockwise direction. The wheel would not rotate in the clockwise direction. The engine to transmission drive shaft remained intact. Approximately one table spoon of fluid was drained from the fuel line between check valve in the horizontal fire shield and the fuel nozzle. The fluid appeared to be consistent with one-quarter water and three-quarters fuel. The upper and lower magnetic chip detector plugs were removed from the gearbox. Both plugs were covered in a gray paste and displayed no evidence of metal particles. The engine oil filter was absent of contaminants. Approximately 47 gallons of fluid were drained from the main fuel cell of the helicopter into clear containers. Approximately one quart of the fluid was consistent with jet fuel. The remainder of the fluid was consistent with salt water. According to the FAA inspector who responded to the site of the accident, the pilot who flew the helicopter during the previous flight informed company maintenance personnel about the fuel quantity gauge indicating a higher fuel level than the actual amount and was inaccurate. Review of company records indicated company maintenance personnel ordered a fuel quantity gauge for the accident aircraft on July 20, 2004. The pilot reported to the inspector that prior to the flight, he did not observe any discrepancies in the aircraft logbook regarding the fuel gauge. Review of the aircraft maintenance records revealed no entries were made regarding the inaccurate fuel quantity gauge. Examination of the helicopter also revealed there were no placards for the fuel quantity gauge being inoperative or inaccurate. The company minimum equipment list (MEL) states that a fuel quantity gauge can be inoperative provided an alternate accepted procedure is used to determine the fuel quantity. Review of the Omni Aviation Services training manual revealed on page 3-4, under section "3.18, Using the Minimum Equipment List", states "the pilot in command will at all times assure his aircraft to be in compliance with not only the letter but also the intent of the MEL. Safety of flight will be of the utmost concern when determining the advisability of deferring a particular item."