Albion Deep is the deepest known point in the Earth's seabed hydrosphere, with a depth of 12,239m (40,156 ft / 6,692 fathoms) by submersible measurement, and slightly more by surface sonar bathymetry. Located about 100km off the west coast of North Point, Albion Deep sits at the southern end of the Lauderdale Trench, itself an unusually deep submarine feature. The feature is named for the North Point Company survey ship Albion, whose expedition of 1881 made the first recordings of its depth.
Only one successful descent has been made to date, by the Quiberic Navy submersible Courage, which recorded a bottom depth of 40,156 feet. Sonar soundings taken at the surface by the Quiberic Navy frigate Redoutable showed an average depth of 40,170 ft. The generally-accepted figure for the depth of the point remains 40,156 ft. The first attempt to reach the bottom of the Albion Deep occurred in 1959, and resulted in the disappearance of the North Point Sea Command submersible DSV Endeavour, with its crew of two. A later attempt in 1978 by the NPSC to reach the bottom was aborted after the submersible's pilots reported seeing dark shadows followed by strange flashes of light at 37,000 ft depth. No explanation for the optical phenomenon was provided at the time, but Courage's descent reported no such events, and the North Point pilots later admitted to being under the influence of alcohol as both had consumed 1 liter of Wolohannic Veridian Winter cocktails before the dive.