Sour, fermented, or off smell
Slimy or mushy texture
Mold on the rind or flesh
Dark, sunken, or wet spots
Flesh is very soft, grainy, or stringy
Unusual discoloration
Bitter, sour, or fizzy taste
Excessive leaking or watery breakdown
Hollow or squishy sound when tapped
Cut watermelon has been stored too long
Rind is cracked with signs of spoilage
Seeds or flesh look unusually dried out or slimy