Santorini is incomplete without descending to its water: the caldera cruise sails inside the drowned crater — climbing live Nea Kameni's hardened lava, swimming the orange hot springs, seeing the cliff and its white villages from below: the angle explaining everything. The sunset catamaran with seafood dinner is the fullest version, the traditional wooden boat the cheapest; sports shoes for the volcano's rough cinder path under open sun; the springs tint light clothes faintly orange — swim in dark.