Well since there was almost a Deinosuchus skeleton in the Fallen Kingdom film it doesn't seem completely out there for prehistoric crocs to be added. It seems like a good fit and it would make enclosures more interesting and diverse. But the main problem I think is that we only have shallow water at the moment. So unless there's a big update or DLC that introduces actual marine animals or at least semi-aquatic animals I don't see this happening any time soon.