Another incredible locale worthy of a day trip, the Similan Islands is an archipelago consisting of 11 islands off the coast of southern Thailand in the Andaman Sea. The archipelago has been protected as a national park since 1982, which helped to limit development and has kept the islands in a more pristine state. The Similan Islands are a dream destination for those who love snorkeling or diving. Beneath the crystal clear waters, you will find some stunning rock formations as well as some of the most beautiful coral growths in the world. On land, the islands consist of low-lying rock overgrown with thick forests. Note that the Similan Islands are closed from mid-May to mid-October every year to help them recover from tourist activity during peak season.