1. existing, happening, or used below the surface of water
2. owing more money on something than it is currently worth
Usage: finance

1. below the surface of water

Examples

• The divers explored the underwater cave system.
• She took beautiful underwater photographs of coral reefs.
• The homeowner was underwater on their mortgage after the market crash.
• The submarine can travel underwater for weeks.
• Fish breathe underwater using their gills.
• The treasure chest lay underwater for centuries.
• Many homeowners found themselves underwater during the housing crisis.