Physically, barnacles resemble little more than a large mouth full of sharp teeth and a thin, but long and very powerful muscular hydrostat combining the functions of a tongue and tentacle, which can be retracted or extended to hang at near-floor level regardless of the animal's height from the floor. The creatures attach themselves to ceilings or the undersides of overhangs, from which they lower their sticky tongues. Although barnacles can be found in a wide array of environments, they seem to prefer damp areas. One curious point is that while many barnacles can be found infesting the Black Mesa Research Facility, fewer are encountered on the species' homeworld of Xen.