Researchers in japan wanted Kaiko to explore the bottom of the Marina Trench and look living things deep in the sea. In fact, the name Kaiko means "trench" in Japanese. The Marina Trench is deep opening in the floor of the pacific ocean, near the Island of Guam. The bottom of the trench is nearly 7 miles(11.27 kilometers) below sea level. compare this depth to the height of Mount Everest, Earth's highest mountain. Everest's elevation is only about 5.5 miles (8.85 kilometers) above sea level.