This sense allows a monster to feel vibrations caused by movement through a liquid. It's an imprecise sense with a limited range (listed in the ability). Wavesense functions only if monster and the subject are in the same body of liquid, and only if the subject is moving through the liquid.
AC 31 (all-around vision); Fort +24, Ref +18, Will +21
HP 195; Immunities acid
All-Around Vision
This monster can see in all directions simultaneously and therefore can't be flanked.
Attack of Opportunity
Trigger A creature within the monster's reach uses a manipulate action or a move action, makes a ranged attack, or leaves a square during a move action it's using.
Effect The monster attempts a melee Strike against the triggering creature. If the attack is a critical hit and the trigger was a manipulate action, the monster disrupts that action. This Strike doesn't count toward the monster's multiple attack penalty, and its multiple attack penalty doesn't apply to this Strike.
Frightful Presence(aura, emotion, fear, mental)
60 feet. DC 27 Will
A creature that first enters the area must attempt a Will save.
Regardless of the result of the saving throw, the creature is temporarily immune to this monster's Frightful Presence for 1 minute.
Critical Success The creature is unaffected by the presence.
Requirements The monster is hiding in water and a creature that hasn't detected it is within the listed number of feet.
Effect The monster moves up to its swim Speed + 10 feet toward the triggering creature, traveling on water and on land. Once the creature is in reach, the monster makes a Strike against it. The creature is Off-Guard against this Strike.
Grab
Requirements The monster's last action was a successful Strike that lists Grab in its damage entry, or the monster has a creature Grabbed or Restrained
Effect If used after a Strike, the monster attempts to Grapple the creature using the body part it attacked with. This attempt neither applies nor counts toward the creature's multiple attack penalty.
The monster can instead use Grab and choose one creature it's grabbing or restraining with an appendage that has Grab to automatically extend that condition to the end of the monster's next turn.
Push
Requirements The monster's last action was a successful Strike that lists Push in its damage entry
Effect The monster attempts to Shove the creature. This attempt neither applies nor counts toward the monster's multiple attack penalty. If Push lists a distance, change the distance the creature is pushed on a success to that distance.