Xestus Sabretooth Blenny

Found singly, close to their burrows, over shallow, sand and weedy areas, of reef flats, and in shallow lagoons.
Juveniles found sheltering with upside down jellyfish.

Coombtooth Blennies are the largest family of bennies, found in both tropical and subtropical waters and freshwater habitats, as the name suggests they have comb like teeth lining their jaws.
Sabretooth Blennies have teeth to match their name!
They can be seen darting forward to sever flesh from fishes fins. (can sometimes be seen taking a swipe at divers as well) They will then dart back into their holes out of harm's way.
Some blennies will mimic cleaner wrasses to get close enough for a nip at fish.
Some Sabretooth Blennies are venomous.