Go to herbivore island (The island) at the right bottom. Go to map if unsure. Look around and you should find some itchyosaurus. But be careful, in the water they look like sharks, don’t mistaken them as sharks they have a pointed snout. Like if you found it helpful! :)
I’m pretty sure they make compy noises. I was trying to tame one and I kept hearing a compy, like really close. But it confused me because compys shouldn’t be underwater but nope, it’s an ichthyosaurus.
(I don’t know if it’s a bug or something but it’s kinda funny)