"Overgrown newt. Like all creatures it has a weak spot between its ears; target its head master!"
Water Serpents are giant snakes that inhabit the waters in and around Heaven's Peak, but most of them are found in Heaven's Peak Understreets. These nasty creatures attack when anything gets to close. They'll linger after a while after they attack, so it gives time for a counter attack. Battling them is best to be done with the Overlord, as it will eat any unfortunate minions that get too close.