Fringehead

...[fringeheads] have a great fondness for empty bottles and cans; the bigger the container opening, the bigger the occupant. In some areas, such as the beer bottle field at the head of Redondo Canyon, southern California, nearly every bottle will house a fringehead. A fish usually lies in its home (which it considers its territory) with just part of its head exposed. Fringeheads are extremely aggressive, and they will lunge at intruders (even divers) with jaws snapping.

This is an excerpt from "Probably More Than You Want To Know About The Fishes Of The Pacific Coast", a most excellent book by Milton Love.