The majority of the Earth's population lives near bodies of water, such as the sea, river, ocean, and lake. The world's most populous cities are located near seas and oceans. Water provides humans with an environment where they can find food. For many people, aquatic animals are the main source of food. People also use water for recreation. They visit beaches, lakes, and rivers to swim, vacation, and simply relax. Approximately 65% of the human body is made up of water. In an embryo, this percentage reaches 95%.