The document discusses the Mariana Trench, the deepest part of the ocean located near Japan. It describes the trench as very deep and cold, with a maximum depth greater than Mount Everest is tall. Survival in the trench would require a submarine, as the immense pressure at its depths would crush any vessel. Few species have adapted to live in the trench, such as anglerfish and crabs, which can survive in the dark conditions below where sunlight no longer reaches.