Truk Lagoon is an atoll in Chuuk state of the Federated States of Micronesia, in the western Pacific, that holds the largest concentration of shipwrecks anywhere in the world, a Japanese fleet of some sixty ships and hundreds of aircraft sunk in two days of American air strikes in February 1944 and now grown over with coral, the greatest wreck-diving site on Earth. The lagoon was the main base of the Japanese navy in the central Pacific, a natural harbour eighty kilometres across enclosed by a reef, and in Operation Hailstone the carriers of the American fleet sank more Japanese tonnage here than in any other action of the war, leaving cargo ships, tankers, a destroyer and a submarine on the sandy floor at depths from a few metres to sixty; the wrecks were forgotten until Jacques Cousteau filmed them in 1969, and they have been diving's cathedral since. The most photographed is the Fujikawa Maru, sitting upright in about 34 metres of water, its deck gun and superstructure fused under decades of soft coral, with fighter aircraft still in its holds and schools of reef fish patrolling the passageways.
Every wreck is a different dive. The tanker Shinkoku Maru carries coral gardens hanging off its masts and railings, with anemones, clownfish and turtles working them, and the San Francisco Maru, deep at fifty metres, has tanks on its deck and trucks in its holds; the holds of others still carry gas masks, sake bottles, shells and the bones of the crews, and the wrecks are war graves treated as such. Several rise close enough to the surface that snorkellers look straight down onto coral-covered masts and gun mounts without diving gear. The islands of the lagoon are green and quiet, with Japanese guns in the jungle and a few dive resorts and liveaboards, and the diving is done all year in warm water. Truk is a fleet that became a reef, and the war is still on the sea floor.