Creature Abilities
Source Alien Core pg. 208
The following creature abilities are listed here because they are shared by many creatures or are highly complex. The statistics for individual creatures might alter the traits, the number of actions, or other rules of these abilities. Anything noted in a specific creature's stat block overrides the general rules for the ability below. In these abilities, “monster” is used for the creature that has the ability, to differentiate it from any other creatures the ability might affect.
Wavesense
Source Alien Core pg. 210
This sense allows a monster to feel vibrations caused by movement through a liquid. It's usually an imprecise sense with a limited range (listed in the ability). Wavesense functions only if the monster and the subject are in the same body of liquid, and only if the subject is moving through the liquid.