underwater

American  

[uhn-der-waw-ter, -wot-er] / ˈʌn dərˈwɔ tər, -ˈwɒt ər /

adjective

1. existing or occurring under water.

2. designed to be used under water.

3. located below a ship's waterline.

---

adverb

1. beneath the water.

   to travel underwater.

noun

1. the water beneath the surface.

   cold currents in the underwater.

2. underwaters, the depths, as of a sea, lake, etc.

underwater British  

/ ˈʌndəˈwɔːtə /

adjective

1. being, occurring, or going under the surface of the water, esp the sea

   underwater exploration

2. nautical below the water line of a vessel

3. (of a stock option or other asset) having a market value below its purchase value

---

adverb

1. beneath the surface of the water

Etymology

Origin of underwater

First recorded in 1620–30; under- + water

Example Sentences

The helmets survived in exceptional condition thanks to a combination of sediment and mineral deposits that formed around them underwater.

From Science Daily • Jun. 8, 2026

We’re sitting on opposite ends of an underwater “sea-saw.”

From Los Angeles Times • Jun. 1, 2026

With its increased military budget, Japan plans to invest in new surface-to-ship missiles and unmanned drones deployed on land and underwater.

From BBC • May 31, 2026

U.S. forces used underwater robots to clear it of mines in the weeks leading up to the operation.

From The Wall Street Journal • May 30, 2026

Most challenging of all was the fact that there was not one person who had ever been involved in an underwater excavation in South Korea.

From "Shipwrecked!" by Martin W. Sandler

Related Words

• submerged
• undersea