sinking

Can refer to one of two things:

• When a character or object is slowly submerging beneath water or a liquid-like substance like mud or quicksand. Depending on the character's situation, this might imply drowning, or they're simply just underwater. Either way, there should be signs that they're descending rather than ascending for air.
• When a boat or submarine capsizes in the water, forcing the crew to "abandon ship".