Sometimes they spawn on the south coast of The Island in that lagoon or on that tiny island with the rock formation near the beavers. Stay on guard! Worrying about Sarcos and the occasional raptor is bad enough.
NEVER and I mean NEVER FIGHT IN WATER. They will stun and all you can do is wait as you see this thing kill your lv 132 triceratops. That has killed rexs. Rip Trixie the triceratops Jan 2020- Mar 2020.