I have vague memories of watching this movie about ten years ago (2008) From my best memories it was from the 70s in color, I think there were a few recognizable 70s faces. About 6 people girls and guys mixed go on a little yatching trip. Some gors missing or dies mysteriously and people get paranoid. They anchor the yatch and go ashore where there is some sort of old temple or cave with nuns of some sort inside. Thats really all i can remember.