There is no substitute for a liveaboard, when choosing your National Park Similans/Surin scuba diving trip. On such a trip you can visit all 30 - 40 dive sites at your own pace.
The Similan/Surin Islands boast some of the best diving that Thailand has to offer. No other region offers such a number of excellent dive sites.
Most travelers visit the Similan/Surin Island Marine National Park for scuba diving and also snorkeling. Distances between these islands are sometimes greater and there are plenty of dive sites between them.