(1) Growing or remaining under water
"Viewing subaqueous fauna from a glass-bottomed boat"
(2) Beneath the surface of the water
- beneath the surface of the water, or of or pertaining to the region beneath the water surface
- beneath the water line of a vessel
- having negative equity; owing more on an asset than its market value
- We've been underwater on our mortgage ever since the housing crash.
- (beneath the water surface): subaqueous
- (having negative equity): upside down