All of the Loyalty Islands are ancient atolls made of fossilized coral, which have been uplifted numerous times, beginning during the Tertiary, forming a series of platforms in a stair-step arrangement, from the sea up to the center of the island. A platform in the center of the island is the original bottom of the ancient lagoon, and the high cliffs along the shoreline are the ancient fringing coral reefs. The porous fossilized coral is well drained, so there are no streams or rivers, but there is a deep fresh water aquifer beneath Lifou. The island of Ouvea has no aquifer, so the inhabitants get their fresh water from a desalination plant.
Because there is no runoff from the islands, the water is crystal clear and the visibility is in the dozens of meters, making for brilliantly clear, in-focus underwater photos. We piled into our catamaran dinghy ALLEGRO and visited some of the underwater caves located in the lee of the high fossilized coral cliffs south of us. Acres and acres of coral shelves spreading out from the bases of the cliffs, support every kind of hard coral you can imagine, in all colors, shapes and sizes, all in excellent condition. We watched fish we had never seen before, both above the coral shelves and in the deep blue waters surrounding the shelves.
Adagio Journal 