Pufferfish can inflate into a ball shape to evade predators. Also known as blowfish, these clumsy swimmers fill their elastic stomachs with huge amounts of water (and sometimes air) and blow themselves up to several times their normal size. 

Some species also have spines on their skin to ward off predators. Even if a predator gobbles up a puffer before it inflates, it won't enjoy the snack. Most pufferfish contain a toxic substance that makes them foul tasting and potentially deadly to other fish. The toxin is deadly to humans. There is enough poison in one pufferfish to kill 30 adult humans, and there is no known antidote.

In Japan, they are called fugu and are a very expensive, delicious treat. They are prepared only by trained, licensed fugu chefs. Most puffers are found in tropical and subtropical ocean waters, but some species live in brackish and even fresh water. Some species of pufferfish are considered vulnerable due to pollution, habitat loss, and overfishing, but most populations are considered stable.

Porcupine fish, any of the spiny, shallow-water fishes of the family Diodontidae, found in seas around the world, especially the species Diodon hystrix. They are related to the puffers and, like them, can inflate their bodies when provoked.

Porcupine fishes are short and broad-bodied, with large eyes, beaklike teeth, and skins set with spines, hence the name. These spines are short and permanently erect in some species, such as the burrfishes of the genus Chilomycterus. In the others, such as those of the genus Diodon, the spines lie against the body except when the fish is inflated. The skins of porcupine fishes, inflated, dried, and sometimes provided with a light bulb inside, are commonly sold as curios. The porcupine fish (Diodon hystrix) is a common and widely distributed member of the family. Found throughout the world, it is a dark-spotted, brownish fish reaching a maximum length of about 90 centimetres (3 feet).