He examines the 'eyewitness accounts' as written in 'The Call of Cthulhu' from a physics point of view. He then states:
In proving the Johansen wasn’t crazy I accidentally figure out that cthulhu is probably real, responsible for the island… and I also figure out what he’s doing down there. Of course, as a brave man of science, I can’t go and admit that Cthulhu exists…Link to the pdf of the article 'Possible Bubbles of Spacetime Curvature in the South Pacific' here.
Via the Miskatonic Museum.