Dagon

Cthulhu lovers take note, this early story of the sea god Dagon is considered to be part of the Cthulhu mythos. In Dagon, the protagonist is lost at sea for days, wading through dead fish and other foulness, until he comes to an island with a monolith on a rocky hillside. After reading the pictographs, his eyes land on the terrible image of a monster rising from the sea. When he wakes up in a San Francisco hospital he thinks the ordeal is over—that is, until the sea god comes to haunt his waking and sleeping life.