Ian's Reef/Flat Rock: Carnac Island, Western Australia, March 2008. Carnac's main claim to fame is that it's home to Australia's largest concentration of Tiger Snakes -- naturally, landing on the island is unadvisable. A number of good dive sites are found around the Island, most in only 4-7 m of water. The reef has many caves and gutters, occupied by a wide range of reef fish and invertebrates. In season, you might also find yourself sharing the water with sealions, as a small colony resides on the western side of the island.