The Blue Holes, Tanna

Tanna's volcanic island is bordered by a plethora of amazing underwater features, ranging from caves to vibrant reefs and jaw-dropping drop-offs. One of Tanna's most popular dives is the Blue Holes, a network of underwater sinkholes and caverns. "This is without a doubt my favorite dive in Vanuatu," Dickson-Smith says. "Several blue holes have names such as Pikinini Blue Hole, Blue Hole One, and Blue Hole Two."

Dives begin at White Grass Ocean Resort's house reef, with the first swim-through taking divers into a blue hole and out the reef wall. "Blue Hole One is a nearly infinite swim-through," Dickson-Smith continues. "A modest entry in the shallows leads through a labyrinth of tunnels that open up into shallow basins, colorful coral gardens, caverns lighted from above through slots, and occasionally out onto the reef wall." These dives frequently feature schools of tuna, fusiliers, and pelagics, as well as whitetip sharks.

Location: Tanna island, Vanuatu