Semiaquatic describes plants or animals that live in or close to the water at least part of the time. Crocodiles are semiaquatic animals, as they spend a lot of time in water but also frequently come onto land.
Semiaquatic is closely related to amphibious, which describes animals, like toads and salamanders, that spend the early stages of their lives in water and much of their adult lives on land. However, the term semiaquatic also refers to plants and animals that mix it up during their whole lives. You might see birds like ducks and geese swimming in a pond or grazing in a field. Semiaquatic plants like mangrove trees, which grow along tropical coastlines, need both land and water to survive.