A Place Under the Ocean APUO

A man is awoken by a series of drops hitting him right on his forehead. He tries to go back to sleep for two seconds, as he is immediately aware of that he is now in a prison cell. The roof has a hole in it, and a stalagtite is pointed directly at his face from above. What kind of underworld creature has detained him and put him in a prison cell in a wet, musky, drippy cave?