The definition of underwater is something that is used or done under water.
Being, living, used, or carried on beneath the surface of the water, esp. of the sea
Growing or remaining under water:
Find another word for subaqueous. In this page you can discover 6 synonyms, antonyms, idiomatic expressions, and related words for subaqueous, like: submerged, subaquatic, underwater, submarine, submersed and undersea.