There's dive sites, and then there's Shark Island. A truly unique place well known for it's many surprises. Large numbers of marine life gets drawn to its reefs since the currents bring large amounts of nutrients from deeper waters.
Shark Island is located to the southwest of Koh Tao, just a few hundred meters from shore. The unique location of the island makes currents quite common here, normally hitting the island from the northeast. Most of the time the currents are manageable but they do get strong at certain times of the year, mainly around the monsoon season from October - December.
Although small enough to circle in one dive, it's more common to dive only parts of the island and have more time to explore specific areas. People most commonly dive the east and northern parts. Here you will find mainly hard corals down to about 16 meters where the sandy bottom leads further out into the deep. Some of these coral areas are quite healthy, mainly due to the currents that not only supply them with nutrients but also keeps the water a little cooler for most of the year.
The south has stronger currents and are sometimes too strong for non experienced divers. However the strong currents means that soft corals thrive here, and the area can boast some of the healthiest soft coral reefs on Koh Tao.
Shark Island from the northwest
It never really gets boring here, as the island has a tendency to attract all sorts of special visitors. On the reef itself you can commonly find large variation of fish, such as titan triggerfish, bluespotted ribbontail ray, harlequim sweetlips and giant groupers. Turtles quite frequently visit, and on occasion you can find giant moray eels. Off the island in the sand large schools of chevron barracudas, one-spot snappers and batfish can be found.
The main attraction however is the seasonal visits of whale sharks. These gentle giants can be seen all year but most commonly visit from late February through to May. Shark Island is always a delight to dive, but when the biggest fish in the sea shows up it's always a special occasion!
Although most people do scuba diving here, it's a great place for experienced snorkelers. The shallow areas around the island has healthy reefs and plenty of marine life and free divers will find large open areas to explore at different depths.
Perhaps the easiest way to get there is to find a dive school that is going diving and you can join in. Most of the dive schools in Shark Bay and Chalok visit there often when conditions are good.
The second option is to simply rent a longtail boat.
The third option is to drive to Sai Daeng beach and rent a kayak. If you choose this option please be aware that the waves, currents and boat traffic in the channel between the beach and the island can be challenging. Please don't attempt this without having experience with kayaking or checking the conditions of the day beforehand.