The Plesiosaur was discovered by the Nektons (though not for the first time) after a volcanic eruption off the coast of Greenland and some strange things happening afterwards. 

Terrifying and unbelievably large, this creature had been hiding in a nearby sea trench for years before the eruption reopened the rift, enabling its release. With impressive jaws that can chomp down on any sized prey, markings that act as camouflage, and 108 meters in length, this creature turned out to be a huge and dangerous encounter for the Nektons