Volcanoes are not something I am normally drawn to as I am to, say, a Caribbean beach or a Parisian café. And swimming in the crater of one wasn’t exactly on my bucket list. But I am drawn to adventure and to stories. As we were looking over the various excursions offered aboard Windstar’s “Treasures of the Greek Isles” cruise, “Sailing the Caldera” appealed to me.  The description — plunging into the green sulfur waters and a Greek lunch served on board — was alluring. The Atlantis mystery made me think that other stories like it would bubble up from the bottom of the caldera’s sea floor.