Puffer fish

Porcupinefish are fish belonging to the family Diodontidae, also commonly called blowfish and, sometimes, balloonfish and globefish. Porcupinefish have the ability to inflate their bodies by swallowing water or air, thereby becoming rounder. This increase in size (almost double vertically) reduces the range of potential predators to those with much bigger mouths. A second defense mechanism is provided by the sharp spines, which radiate outwards when the fish is inflated