Tongan Fangblenny

Found over shallow waters of coral and rocky reefs, often seen in the water column feeding.
Pacific Ocean - Tonga

Combtooth Blennies are the largest family of blennies, found in both tropical and subtropical waters and freshwater habitats, as the name suggests they have comb like teeth lining their jaws, well suited for scraping food off hard surfaces!
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.
A few Sabretooth Blennies are venomous.