Koh Samui is a good starting point to discover scuba diving. There are many dive schools scattered over the island offering all PADI courses from Bubblemaker to dive master. On Samui you will mostly learn the basics and first steps of scuba diving while the actual dives will take place near the surrounding islands like Koh Tao or the Angthong National Marine Park.

Most dive schools have their own boats and will offer daily dive trips for beginners and professionals but of course you can join them for just a snorkeling trip.