I just read this:
Oldest Sea Creatures Have Been Alive 4,000 Years
It reminded me of my previous post (above) and made me think- depending on how you think of corals mechanically (IOW, if they can be targeted by "Awaken"), you could potentially have some truly alien and powerful intellects in the deep waters of the world. Possibly even a challenge to Aboleths and the like.
Coral colonies, as I recall, grow by cloning themselves. Imagine, if you will, a coral polyp being awakened, then cloning itself over and over again, for thousands of years...a colony of intelligent clone-siblings.
A coral colony could be a truly formidable opponent, especially if the sedentary lifestyle of coral is unsatisfactory to the awakened polyps...and they go insane.
OTOH, they could also have quite a sophisticated culture.
Possibilities. Possibilities...
One key problem is that coral colonies are, well, stuck. They can expand, slowly, but they can't really move themselves once they are established. Awakened or not they simply lack the physical means. As for what a coral intelligence might be like, Corey Doctorow has a story that addresses that somewhat. At least, I know I read a story like that and I think Corey Doctorow wrote it. His stuff is CC, so check out "I, Rowboat". I think that's the right story. Even if it isn't it's good and should be freely available to you.