Find all the best Nature Reserves here with us Game and Nature Bikini Atoll is an atoll in the Marshall Islands which consists of 23 islands totaling 3.4 square miles surrounding a deep 229.4-square-mile central lagoon. Arno Atoll is a coral atoll of 133 islands in the Pacific Ocean, and forms a legislative district of the Ratak Chain of the Marshall Islands. Its total land area is only 5 square miles. The Kalalin Pass Majuro is one of the most majestic dive spots in all of the Marshall islands. The site is known for its beautiful corals and fish.