the watcher in the water

[Cazoz]

There is no conclusive proof of this either. The spiders, such as Shelob and certainly Ungoliant (!) were not created by Morgoth. And they were pretty nasty. We cannot presume that simply 'good' animals were made naturally, and that all nasty ones were the creation of Sauron and Morgoth.

There's nothing really written about the Watcher at all. The fact that it's referred to as that could be inferred that it was anomalous, as otherwise a species or more specific name might have been given somewhere else. Thus we can only really say it it was a one-off creature, and even this is presumption.