Khao Lak is the closest and most convenient departure point for diving and snorkelling trips to the awesome national park islands of Ko Similan, which can be reached in three to four hours on a live-aboard or other large boat or in two hours in a much less comfortable speedboat. The islands are currently only open from approximately November to April and all divers have to pay a one-off national park fee of B400 plus a B200-a-day diving fee, usually on top of dive-trip prices. Local Khao Lak dives are generally possible year-round, especially the highly rated wreck of a tin-mining boat near Bang Sak, which is especially rich in marine life such as ghost pipefish, moray eels, scorpion fish, nudibranchs and yellow-tail barracuda. All Khao Lak dive shops also teach PADI dive courses, with the last two days of the Openwater course often done on location in the Similans.
Swiss–Thai-run PADI Five-Star Centre that specializes in one-day dive trips to the Similans, on a big dive boat (B4700 plus equipment; B2800 for snorkellers). Their Openwater courses cost B17,000 with two days spent diving the Similans.
Sea Dragon Dive Center
Highly recommended PADI Five-Star Instructor Development Centre which has three live-aboard boats – including budget and deluxe options – running frequent three-day trips to the Similans and Ko Bon (from B11,900 including equipment), and four-day trips to the Similans, Surin islands, Ko Bon, Ko Tachai and Richelieu Rock (from B17,900). Snorkellers get about one-third off. Also offers local wreck and other dives (starting from B1000, not including equipment, for a two-tank dive) and PADI dive courses: the four-day Openwater is B9800, or B15,900 (plus B1200 national park fees) with two day-trips diving the Similans.
Highly recommended three-day live-aboard snorkelling trips to the Similans (B8200). Current departures are twice weekly on Tuesdays and Fridays, from roughly the end of October to May.