The name of the Latin-script letter U.
A thing in the shape of the letter U
(abbreviation) you (in text messaging and internet conversations)
Take me with u.
Beneath the surface of the water, or of or pertaining to the region beneath the water surface
Beneath the water line of a vessel
Under water.
Having negative equity; owing more on an asset than its market value
We've been underwater on our mortgage ever since the housing crash.