Rina Cave opens onto the Aegean three kilometres south of Kalandos, its entrance invisible from land until a boat rounds the final promontory and the arch materialises in the limestone face. The cave system extends forty metres into the cliffside, carved over millennia by wave action and tectonic shift that lifted the Cycladic basement rock and left it vulnerable to erosion. Geologists date the visible striations to the Pliocene, when sea levels fluctuated and left terraced shelves now submerged at high tide. The chamber's ceiling rises twelve metres at its apex, high enough that light penetrates twenty metres inward during the midday hours of summer, turning the water a refracted cyan against white stone. The cave became a waypoint for fishermen from Kalandos and Panermos in the nineteenth century, who sheltered here during sudden squalls and carved mooring notches into the rock face. By the mid-twentieth century, local captains began ferrying visitors from Naxos Town and Agia Anna, recognising the site's appeal as boat traffic to Koufonisia and the Small Cyclades increased. Today, boat trip to rina's cave tours depart from multiple harbours along Naxos's southern and eastern coasts, often paired with stops at Koufonisia or Iraklia to form half-day or full-day itineraries. The cave remains undeveloped — no jetties, no lighting, no constructed pathways — and accessible only by sea, a condition that has preserved its raw geology and limited visitor numbers to those willing to board a vessel. Inside, the acoustic properties amplify every sound: the slap of waves against stone, the echo of voices, the drip of condensation from the ceiling's apex. The water within the cave averages four metres deep near the entrance, deepening to seven metres at the rear chamber, where sunlight fails and the temperature drops three degrees. Swimmers enter from the boat's swim platform, the salt content high enough to buoy even reluctant swimmers, and drift beneath the overhangs where swallows nest in the warmer months. The rock face bears fossil imprints of marine organisms — bivalves, gastropods, echinoids — visible to anyone who swims close and looks upward at the striations. Guides on boat trip to rina's cave excursions typically allow twenty to thirty minutes inside the cave, enough time to swim the length, photograph the vault, and return to the deck before continuing to the next anchorage.