Heian Maru

The largest wreck in the lagoon. The Heian Maru was a Japanese ocean liner converted to a submarine tender, and at over 150 metres she is the biggest of all the wrecks sunk at Truk in the 1944 raid. She lies on her port side in the sheltered lagoon, her vast hull a landmark dive that rewards several visits to take in fully.

Torpedoes, periscopes and lettering. As a submarine support ship she carried spare torpedoes and periscopes, and these still lie in and around her holds, along with shell casings and machinery. The ship's name picked out in raised characters on the hull is a favourite sight, a rare legible signature on an otherwise anonymous field of wrecks.

Depth and access. The wreck spans roughly 12 to 34 metres, with the uppermost side within easy recreational reach and the deeper holds and interior suited to divers with wreck-penetration training. Advanced Open Water certification is a sensible baseline; the sheer length means dives are planned in sections along the hull.

A reef on a giant. Coral and sponges cloak the exposed plating, and reef fish shelter in the superstructure. Lying on her side, the Heian offers dramatic swims along the deck rails and into cavernous holds. She is dived year-round, with the calmest and clearest conditions generally in the drier winter and spring months.