Package tours for snorkeling, diving, elephant riding etc. are widely available.

Thaifun day cruise to southern islands. Relaxing and snorkeling. Very nice crew on board.

Khlong Plu waterfalls is medium size waterfall within a half a mile walk from parking area. Swimming possibility. Entrance fee to park 400 baht.

Ploy Scuba Diving come to the best dive sites with speedboat. All PADI Course / Diving Trips / Snorkelign Trips. ploy.travel@gmail.com

Snorkeling and Diving Koh Chang is maybe not the best diving spot in Thailand, but diving around Koh Chang gives some adventurous feeling

See Fireflies Boat trips on the lagoon near Khlong Prao beach to see fireflies can be organised through a travel agent/hotel. Year round. 150-200 baht for 30 minute trip.