Sam's beach ball was buoyant, so therefore it

1. was lost.
2. would not sink in the water.
3. was out of air. 

buoy•ant

Pronunciation: (boi'unt, bOO'yunt), [key] 
—adj. 
1. tending to float in a fluid. 
2. capable of keeping a body afloat, as a liquid. 
3. not easily depressed; cheerful. 
4. cheering or invigorating.