Here's a great article about the past, present and future of one of the bays on Koh Tao. I have snorkelled and dived there and it is a pretty amazing place.
This is the bay where I for the first time in my life had the fantastic privilege to see the majestic and wonderful creatures, the sharks.
http://www.newheavendiveschool.com/articles/present-future-koh-taos-shark-bay/