Nessasaur

One massive queen that controls all other of her species in a body of water; immortal and sentient. When a flipper is lost, the flipper will grow into a new nessasaur over the span of a month. The adult nessasaur that lost the flipper will regrow it in the same amount of time.   Flipper must remain intact.   Average lifespan of 90-100 years   Size adjusts to the body of water, ranging from great dane to blue whale.   Instructed to spread to other bodies of water.  

Queen & Thot Nessie

(if she swims she's a thot) Thot Nessie is also sentient, but capable of granting sentience to others with a touch.  The two are unable to come within (???) miles of one another without catastrophic consequences. Reality itself will rebel against this.