There are currently about 7 billion people on the planet, all of which require water to survive. Even without the direct consumption of water, water is usually in most other beverages that people consume. Also, many of these billions of humans use massive amounts of water everyday to do laundry, bathe, wash dishes, and so forth. Many animals require water to survive as well.
Also, humans and animals requiring frequent water consumption has been a thing for billions of years. Obviosuly Earth’s water supply is not infinite. How have we not already exhausted all the water the Earth has to offer?
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A water cycle exists in which water evaporates from lakes, rivers, and oceans, but the water vapor in the atmosphere eventually condenses and falls as precipitation. This is constant, so there is always water flowing in rivers and lakes have relatively stable levels. Consumption of water by organisms is temporary, and water leaves the body by peeing, sweat, and vapor during respiration. So its residence inside organisms is temporary, and it eventually goes back into the water cycle. There are a few cases where humans have exhausted local water supplies, but the cycle is global.
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