Ao San Beach is a great beach to swim with a mask and fins. A lot of marine life. The beach is small and, recently, has become quite famous, so it can be crowded. There is a restaurant and rental of swimming accessories. Travel to this beach via the hotel at the right end of Nai Harn Beach. Yanui Beach is the southernmost of the island's kupable beaches. A small but very pretty beach under the mountain by the windmill. There are several cafes across the street from the beach. A great place to swim with a mask and fins. Siam Beach is a great place for snorkeling. Lots of starfish and colored fish + rock Passage to the beach through the Sabai Corner Hotel. The entrance is 50 baht.