Water is a precious resource, and all things need water to survive.
All organisms, like animals and plants, use water: salty or fresh, hot or cold, plenty of water or almost no water at all. They are adapted to all kinds of habitats, from sizzling deserts to the freezing, pitch-dark ocean floor. The first living things appeared in the ocean nearly four billion years ago. Some, like our ancestors, adapted to life on land. Humans have figured out how to survive in swamps, deserts, and all kinds of habitats in between.
The ocean is still home to more kinds of life than anywhere else on the planet.