The tide differentials in the Kimberley are among the greatest in the world. The phenomenon of the 140 square mile reef system known as Montgomery Reef is the product of the Kimberley's tide differentials, which can be as much as 26-30 feet. Unlike Atlantis which sank to the bottom of the sea and stayed there, twice a day as the high tide goes out, Montgomery Reef emerges from the sea. The expedition arrives at low tide as the reef becomes visible. There is the opportunity to walk on the reef and see the corals. Incredibly, even though the corals are exposed to the sun every day, the corals suffer no adverse affects. Scientists have-discovered that this is because the corals secrete a mucus sunblock with an SPF of 45. Montgomery Reef is truly fantastic.