We arrived in the little town of Luganville on the northern Vanuatu island of Espiritu Santo with only a vague idea of how we wanted to spend our time, but we knew there were some great scuba diving spots around the island (including the WWII-era shipwreck of the USS Calvin Coolidge), a few sandy beaches worth seeing (how could a place called Champagne Beach not be beautiful?), and one crazy cave that Lonely Planet highly recommended we check out.