Most deep, deep parts of the ocean are not explored because there is no light in the midnight zone or deeper. It is freezing cold, and the air pressure is waaay too extreme. (8 TONS per square!), so most creatures of the deep are unheard of, or have been heard of and live peacefully in the dark. Only two people have gone to the dark zone, and live to tell the tale. The deepest fish ever found was in the Puerto Rican Trench. That Trench is so deep, that Mount Everest could sink in it,( Mount Everest is over 8,846 meters tall!) and there would still be 1069 meters to the top!