On the west side of Koh Taen in a mangrove forest, with a well-built boardwalk runnng through it so you can ge close to nature. You'll be amazed at how quiet it is on this island. There are no cars or motorbikes, and with no electricity, there aren't even any boom boxes blaring. It can be all thmazing given that you can be back in your hotel room in a half an hour or so after leaving the island.
Very few local tour operators offer trips to Koh Taen. If you want to try it on your own, you will need to make your way to the fishing docks at Thong Krut, then negotiate with one of the boats to take you there. See the Samui map for a general idea of where