Palau, a tiny island nation in the middle of the western Pacific ocean, is a land of giants. Large manta rays soar through its azure seas. Massive Second World War wrecks harbor dark secrets on the ocean floor. The archipelago is surrounded by a colossal underwater trench that reaches more than half a mile down into unseen depths. Its reef, one the largest living structures on the planet, is home to more than 1,500 species of fish.