Which fishes blow themselves up like balloons?
Porcupine fish and puffer fish look like normal fish most of the time. When they are threatened by another fish or perceive danger, they swallow water and inflate their bodies into a ball shape—up to five times their normal size. Predators see this and are scared away, and the enlarged size makes it difficult for larger predators to eat them. When the fish senses that there is no longer any danger, it slowly deflates.