Porcupinefish also called blowfish and balloonfish, and often confused with pufferfish, this is because they are related to pufferfish and are very similar in appearance.
They are found in shallow warm water and tropical seas worldwide, so the waters around Koh Tao are perfect for them with an average temperature of 29-30 degrees all year round, you can see them at almost all of the divesites around Koh Tao, quite often hiding near the coral, and usually swim slowly. The Porcupinefish is very shy and usually hides when divers approach.
As a defense mechanism they are able to inflate their body by swallowing water or air, increasing to almost double in size so they appear larger to predators, and while inflated the spines covering their body stick out. Some species of Porcupinefish can be poisonous, this poison is often thought to come out from their spines to defend themselves, but this is not true. They have what is called a Tetrodotoxin in their internal organs, which makes them poisonous. As a result of these defenses they have very few predators. They aren’t considered dangerous to humans, unless when eaten.