Below is a link for some blow hole photos. It is really neat. However, I had been visiting the Island for a year before I ever saw it. Usually there was just a stiff breeze coming out of the hole.The taxi drivers always said, well, maybe Monday, maybe tomorrow, etc... I think it is more seasonal. It is well worth seeing if you get the chance. In addition to "The Blow Hole" there are lots of smaller ones.
Capt Morgan's Cave is pretty boring. If you do visit, ask the old lady if she knows anything about Flint, Michigan.