A series of rock arches, tunnels and blow-holes you swim through, packed with glassfish and grouper, plus the mosaic floors of…A series of rock arches, tunnels and blow-holes you swim through, packed with glassfish and grouper, plus the mosaic floors of a Roman villa on the shore above and amphora scatters on the seabed below. Giannutri was a Roman waypoint, the Domitii Ahenobarbi built a villa here in the 2nd century AD, and its harbour served the grain route. The island is also where the Costa Concordia passed the night before she struck Giglio in 2012. Anchorage: Anchor in Cala Maestra or Cala Spalmatoio depending on the wind; the island is a natural stop between Giglio and Argentario. Hazards: Overhead swim-throughs, and the Nasim II wreck on the north side is a deeper technical dive. Plus