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 a series first, Captain Sig Hansen launches an unprecedented covert scouting mission, deploying an underwater drone into the unknown waters in a bold attempt to locate the rare strain of king crab before the rest of the fleet arrives. —Tony Maglio, HollywoodReporter, 23 Apr. 2026

Programs like the Orca unmanned underwater vehicle and Hammerhead anti-submarine mines further show growing interest in this domain. —Sujita Sinha, Interesting Engineering, 23 Apr. 2026

Prior to 2019, only four underwater archaeological sites were known in the area, and only one of those could be considered the result of a shipwreck, according to the researchers. —Amarachi Orie, CNN Money, 22 Apr. 2026

Kimberly Jeffries is an underwater cinematographer and photographer based in Hawai’i, known for her work in marine conservation and diving. —Photovogue, Vogue, 22 Apr. 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