People have always wanted to discover new things and new worlds. We have built spaceships to go to other planets and are planning to visit other galaxies one day. Meanwhile, we know very little about our own planet. The oceans, which cover 70 percent of the planet, are an unknown world to us. The Pacific Ocean is the largest one. The lowest point on the Earth is also there. It is called Challenger Deep and it was discovered in 1875. The Pacific Ocean stretches from the Arctic Ocean to the coast of Antarctica, but most of its water is in the warm tropics, which makes it warm. A lot of fish and animals live in the Pacific Ocean. The place is still waiting for researchers to discover its secrets for us.