I encountered this Gosline’s fang blenny recently while snorkeling. It seemed to be curious about me, swimming in my direction and then turning away. Perhaps it was thinking about taking a bite out of me, because that’s what these fish do. They bear a resemblance to juvenile Hawaiian cleaner wrasses, which clean larger fish. These blennies use this similarity to sneak in and take a bite out of the bigger fish.
And what about the name? These blennies have fangs on their lower jaws that they use to bite the inside of the mouth of any predator that grabs them. It’s usually enough to cause the predator to spit them out.