What kind of fish can blow itself into a prickly balloon?

The fish that can blow itself into a prickly balloon is the pufferfish, also known as fugu. When threatened, it swallows water (or air) to inflate its body, making it appear much larger and more intimidating to predators. Its skin contains toxins that can be lethal, adding to its defense mechanism. Several species of pufferfish possess this unique ability.