Sec du Caldanu is a classic Corsican sec with drop-offs, rocky shelves, and plateaus that keep the route varied. It suits intermediate to advanced divers who want steady scenery rather than a single headline feature, and the relief makes slow turns and repeated passes worthwhile. Expect a Mediterranean mix of groupers, lobsters, moray eels, and other fish in clear water when conditions are settled. Plan it as a boat dive from the Calvi-Lumio side so you can time the site with calmer seas.