underwater

adjective

un·​der·​wa·​ter ˌən-dər-ˈwȯ-tər 

-ˈwä-

1

: lying, growing, worn, performed, or operating below the surface of the water

underwater plants

2

: being below the waterline of a ship

3

a

: having, relating to, or being a mortgage loan for which more is owed than the property securing the loan is worth

homeowners who are underwater on their loans

b

: having, relating to, or being a stock option for which the price of the option is higher than the current market value of the stock

underwater adverb

Synonyms of underwater

• aquatic
• submarine
• submerged

Examples of underwater in a Sentence

underwater plants don't require as much light to grow as surface plants

a vessel designed for underwater exploration

Recent Examples on the Web

In early 2021, anchors from large container ships hooked an underwater oil pipeline on the ocean floor some 5 miles off Huntington Beach’s coast, bending it like a straw. —Teri Sforza, Oc Register, 28 May 2026

At this year’s Venice Biennale, the performance artist and choreographer Florentina Holzinger used the stage of the Austria Pavilion to alert viewers to an increasingly underwater dystopia. —Lilyanna D'amato, ARTnews.com, 28 May 2026

The Island of Hawaii features three famous volcanoes — Kilauea with its spectacular eruptions, Mauna Kea and its spectacular sunsets, and Mauna Loa, the world’s highest mountain when measured from its underwater base to the summit. —Joe Yogerst, Forbes.com, 28 May 2026

Any natural light would trigger biological growth in the water, compromising underwater visibility, already one of the hardest variables to manage during testing. —Deena Theresa, Interesting Engineering, 28 May 2026

Word History

First Known Use

1627, in the meaning defined at sense 1

Rhymes for underwater

• imprimatur
• auteur
• blotter
• cotter
• daughter
• hotter
• mater
• otter
• plotter
• rotter
• slaughter
• spotter

Kids Definition

underwater

adjective

un·​der·​wa·​ter ˈən-dər-ˈwȯt-ər 

-ˈwät-

: lying, growing, worn, performed, or operating below the surface of the water

underwater plants

an underwater cave

underwater

-ˈwȯt-, 

-ˈwät-

adverb

Legal Definition

underwater

adjective

un·​der·​wa·​ter

1

: owing more on a mortgage loan than the property securing the loan is worth

underwater homeowners

2

: being or relating to a mortgage loan in which more is owed than the property securing the loan is worth

underwater mortgages

underwater properties