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

Ponta do Ouro's warm waters offer some of the best diving spots in Africa, with plenty of coral reefs, whale and reef sharks, turtles, dolphins, and rays—plus, great visibility, a real perk for underwater photographers. —Melanie Van Zyl, Travel + Leisure, 6 Mar. 2026

Retreat was most pronounced where deep underwater pathways funnel warm ocean water toward the base of glaciers, Rignot said. —Sharmila Kuthunur, Space.com, 4 Mar. 2026

According to a new report, more than 25% of new-car buyers in the United States are underwater on their existing car loans. —Byron Hurd, The Drive, 4 Mar. 2026

The new boats are being built to replace older submarines that have been in service since the 1980s, strengthening the navy’s underwater capabilities for the future. —Jijo Malayil, Interesting Engineering, 3 Mar. 2026

Word History

First Known Use

1627, in the meaning defined at sense 1

Rhymes for underwater

• annunciator
• imprimatur
• backwater
• bathwater
• blackwater
• breakwater
• deepwater
• edgewater
• feedwater
• floodwater
• freshwater
• granddaughter

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