Espiritu Santo — SS Coolidge

Dive centres in Luganville run the site as a shore operation: a short drive east of town, kit assembled beside the truck, then a walk in over the shallows and a descent down the sloping seabed until the hull comes out of the gloom. Profiles are deep and the ship is long, so a normal day is two dives with a long surface interval between them. Guided dives commonly incur staged decompression, and operators tend to hang deco cylinders on the ascent line as standard rather than as an upgrade.

She lies on her port side with the bow toward shore, so depth increases steadily as you work aft. That geometry shapes the whole trip: the forward end tolerates long, unhurried dives, while anything toward the stern buys minutes rather than hours. Inside, the layout of the liner is still readable in corridors, holds and public rooms, overlaid with the military fit-out she was carrying. Fine silt is the main hazard, so penetration routes are dived in a set order, on lines and with lights.

She struck American mines guarding the channel in October 1942, and accounts still differ over why the warning never reached the bridge. The captain ran her onto the reef, and all but two of the roughly 5,000 men aboard got off before she slid down the slope and sank. What that left is a ship that went down loaded, which is why divers book a week here rather than a day: each dive takes a different route through a different part of her, and the ban on removing anything keeps the interiors worth swimming through.

It suits divers who want depth, structure and repetition more than reef variety, and who are content to dive one wreck a dozen times over. Those with decompression training get the whole aft end to work with; anyone happiest in shallow coral will find the surrounding bay quiet by comparison. Night dives and the shallower sites along this stretch of coast break up the decompression load, and because the channel is sheltered, lost days are rare outside the cyclone months at the turn of the year.