Porcupinefish

Porcupinefish drift slowly over An Thoi's coral gardens, their large expressive eyes and permanently surprised expression belying their effectiveness as predators of sea urchins, mollusks, and crustaceans, which they crush with powerful fused beak-like teeth. When threatened they inflate their body to three times normal size by swallowing water, erecting hundreds of sharp spines that make them nearly impossible to swallow. Their predation on sea urchins helps prevent urchin outbreaks that would otherwise graze the reef bare of crustose coralline algae critical for coral recruitment.