Titanic was long thought to have sunk in one piece and, over the years, many schemes were put forward for raising the wreck. None came to fruition.[212] The fundamental problem was the sheer difficulty of finding and reaching a wreck that lies over 12,000 feet (3,700 m) below the surface, in a location where the water pressure is over 6,500 pounds per square inch.[213] A number of expeditions were mounted to find Titanic but it was not until 1 September 1985 that a Franco-American expedition led by Robert Ballard succeeded.