Aquatic means living in, happening in, or relating to water. Fish, dolphins, and octopuses are aquatic animals because they spend almost their entire lives in water. Water lilies and seaweed are aquatic plants. When you swim laps at an aquatic center, you're using a facility built around water activities.

You'll see it used to describe anything connected to watery environments: aquatic ecosystems like coral reefs, aquatic sports like water polo, or aquatic insects like water striders that skate across pond surfaces.

Some animals are semi-aquatic, meaning they live partly in water and partly on land. Beavers, otters, and crocodiles are semi-aquatic: they're excellent swimmers but also spend significant time on shore. Frogs start as fully aquatic tadpoles with gills, then transform into semi-aquatic adults with lungs.

When scientists study aquatic life, they're examining the incredible diversity of creatures that have adapted to underwater living, from microscopic plankton to massive blue whales, each specially adapted to their watery world.