Books, Articles, et cetera on Underwater NHI?

Long story short, I'm a casual researcher that runs a podcast that covers, among many other things, UFOs and Aliens, and on our next episode, we are planning to dedicate a full discussion revolving around USO's and possible NHI bases hidden in the oceans. I cast a wide net when I do my research, and we've at least brushed on some of the more popular stuff in the past (Bill Cooper and his book, some of the recent hearings from Naval personnel, et cetera.) I'm always looking for books to read o...