Earlier one spawned at my base and scared for my creatures I started to attack in in the water with a plesiosaur.It was about 30 minutes of luring it into the water and biting it and repeating,eventually it started to run onto land as it was low.I then led my strongest rex and Giga on a high pursuit chase.I eventually killed it when it got stuck and I killed it with ascended sword.

The reasoning of this was it killed the dolphin I had since almost day 1