underwater
UK: ˌʌndəˈwɔːtə | US: ˌʌndərˈwɔːtər
adj. located, occurring, or used beneath the surface of water
adj. designed or equipped to operate underwater
n. the realm or environment beneath the surface of water
The word "underwater" is a straightforward compound of "under" (Old English under, meaning "beneath") and "water" (Old English wæter). It emerged in Middle English to describe anything existing or functioning below the water's surface. The morphemes retain their original meanings, reflecting the logical spatial relationship between the two elements.
The divers explored the underwater cave system.
This camera is waterproof and designed for underwater photography.
Coral reefs thrive in the vibrant underwater ecosystem.
The submarine can remain underwater for months.
Scientists study underwater volcanoes to understand tectonic activity.