Which fishes blow themselves up like balloons?

Porcupinefish are members of the family Diodontidae (order Tetraodontiformes), and are also known as blowfish, balloonfish, and globefish. They are often referred to as pufferfish, although this is not to be mistaken with the visually similar and closely related Tetraodontidae, which are more usually referred to as pufferfish. Most of the time, porcupine fish and puffer fish appear to be ordinary fish.

They ingest water and inflate their bodies into a ball form, up to five times their regular size, when threatened by another fish or detect danger. Predators are scared away when they notice this, and their expanded size makes it harder for larger predators to devour them. When the fish realizes there is no longer any threat, it gradually deflates.