Mystery Island — known locally as Inyeug — is a small, flat coral cay just offshore from Anelgauhat Bay, ringed with white sand and excellent reef. It is uninhabited, which means when the cruise ships are gone (usually by mid-afternoon) you can have it almost entirely to yourself.
The snorkelling directly off the beach is outstanding — the reef starts in just a few metres of water and the fish life is dense. The island is small enough to walk around in about 20 minutes. There is no freshwater and no shade beyond the beach trees, so bring what you need. Getting there from the main island requires a local boat.