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

Dedicated snorkelers and divers will do better to book a trip for the drier months between December and April, when unbeatable underwater visibility gives Ambergris Caye some of the clearest waters in the world. —Carley Rojas Avila, Travel + Leisure, 30 Nov. 2025

The deep blue lighting draping the entire lower floor also gives the room an underwater feeling, which is contrasted with a never-ending loop of fireplace videos playing on the many televisions attached to the walls. —Kansas City Star, 29 Nov. 2025

The story is narrated by Professor Pierre Aronnax and includes plenty of underwater exploits and proper dramatic beats that explore man's relationship with nature, political resistance, and the weight of hate and revenge. —Fran Ruiz, Space.com, 29 Nov. 2025

One of the biggest and newest undersea drones in Western militaries is the Ghost Shark, an extra-large autonomous underwater vehicle (AUV) developed by the Australian military and defense tech newcomer Anduril. —Brad Lendon, CNN Money, 27 Nov. 2025

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