You might enjoy some H.P. Lovecraft, although I can't remember which ones feature Chthulu most. I like your photos fromt eh Great Barrier Reef - this makes me want to go there. I'll see if we have any pictures from snorkeling in the Sea of Cortes in Mexico, but I think all the photos are from land.
Cthulhu is a mythical god from the stories of H.P. Lovecraft, a horror writer from the 20's and 30's. A lot of us who are ceph nuts are also fans of Cthulhu and HP Lovecraft in general. I would suggest picking up the collection of short stories, Bloodcurdling Tales of Horror and The Macabre for a good introduction to his work.