The SS President Coolidge, Espiritu Santo

The Coolidge is one of the world's largest wrecks, measuring slightly over 200m (656ft) in length. The Coolidge was sunk in 1942 during WWII after it collided with a friendly mine. It became stranded on a steep sandbank and slid down to where the wreck currently sits 30m (98ft) below. It takes several dives to investigate the full former luxury liner converted troop transport and acclimate to the wreck's deepest point of 70m (230ft).

"Divers come to Vanuatu just to dive the Coolidge, and spend the best part of a week doing so, starting with an orientation dive and working their way down to The Lady – a porcelain figure riding a unicorn in the first class dining room – and on to the engine room and the stern, the wreck's deepest point," Dickson-Smith says. The aquatic life on this wreck is a highlight, with a huge resident moray eel named Nessie and the spotlight fish in Cargo Hold Two."

Location: Espiritu Santo, Vanuatu