The deep sea or deep layer is the lowest layer in the ocean, existing below the thermocline and above the seabed, at a depth of 1000 fathoms or more. Little or no light penetrates this part of the ocean, and most of the organisms that live there rely for subsistence on falling organic matter produced in the photic zone. For this reason, scientists once assumed that life would be sparse in the deep ocean, but virtually every probe has revealed that, on the contrary, life is abundant in the deep ocean. In 1960, the Bathyscaphe hello'Trieste descended to the bottom of the Mariana Trench near Guam, at 10,911 m, the deepest known spot in any ocean. If Mount Everest were submerged there, its peak would be more than a mile beneath the surface. After the Trieste was retired, the Japanese remote-operated vehicle Kaikō was the only vessel capable of reaching this depth until it was lost at sea in 2003.