The small Koh Taen island (you will also often find the name of Koh Tan but it is pronounced 'go tèn' so this spelling is more correct) is about twenty minutes by boat from the south of Koh Samui island opposite to Thong Krut or Bang Kao, the two departure points of the longtails boats to get there. Very close to Samui, this is the number one destination for snorkeling around Ko Samui. The island is bordered by a reef where many multicolored fishes live.
A little further on, Koh Matsum (or Koh Madsum) offers pretty beaches with a lagoon with turquoise waters. On the main beach, there is a small bar where the longtails boats systematically drop you, a little sad as there are much more deserted beaches on the other side of the island. The purpose of this excursion is, as for me precisely, to make an tour away from mass tourism. There is also a cave with giant bats on one of the two islands.
You can visit Koh Taen and Koh Matsum by yourself. Just go to Thong Krut in the South of Koh Samui. Almost all seaside restaurants there offer boat trips to this islands. Count 1500 THB per boat, regardless of the number of passengers. For this price, you will have a 2-3 hours excursion with a snorkeling stop off Koh Taen (mask and snorkel provided by the captain of the boat) and a moment on the main beach of Koh Matsum (the one with the bar where renting a longchair costs 100 THB and where you can also rent kayaks).
Longtail boats make the minimum by default, it's nice (that's what I did) but Koh Tan and Koh Matsum islands have more to offer. Try to negociate with them to see more.
Offered in English The small Koh Tan island is half an hour by longtail boat from Koh Samui. Prestine sand beach, seabed with multicolored fish, mangroves, temple..., with its neighbor Koh Matsum and its wild pigs, it offers a nice setting for a day trip from Samui.
Offered in English This offer invites you to discover the interior of Koh Samui island, its fruits plantations, a secret waterfall, the local life, amazing viewpoints and will finish the afternoon by taking you to a small neighboring island for snorkeling, an barbecue, local rhum drinking, relaxation and swimming.