In the water
Snorkelling, Diving and Similan Liveaboards
Day-trip snorkelling, scuba day trips and multi-night liveaboards reach different parts of the park. Which matches what you want to see.
Check dates and availability ↗Ways to experience the Similan Islands underwater
| Trip type | Duration | Typical reach | Sleeps |
|---|---|---|---|
| Snorkelling day trip | One day | Islands 4, 8 and nearby snorkel stops | Back on the mainland |
| Scuba day trip | One day, usually 2–3 dives | Similan sites; some run to Koh Bon | Back on the mainland |
| Liveaboard, Similans only | Typically 3–4 days | Similan sites plus Koh Bon | Aboard, moored offshore |
| Liveaboard, Similan + Surin | 4 days / 4 nights, around 11 dives | Adds Koh Tachai and Richelieu Rock | Aboard, moored offshore |
| Diver supplement | 200 THB per diver per day | Charged on top of park entry | — |
Snorkelling reaches more than you would expect
The Similans are unusually generous to snorkellers because much of the coral sits shallow. Standard day trips build around several in-water stops off the eastern side of the chain, where gentle coral slopes start close to the surface, plus beach time at Ko Miang and Ko Similan. You are not getting a watered-down version of the diving; the eastern reefs are genuinely the shallow ones. What you will not see from the surface are the western granite formations, the swim-throughs at Elephant Head Rock, or the deeper cleaning stations where mantas appear.
Scuba day trips from the mainland
Dive centres in Khao Lak and Phuket run single-day Similan trips, usually two or three dives, returning the same evening. They reach the classic Similan sites, and some itineraries push north to Koh Bon. The appeal is obvious: no multi-night commitment and no cabin. The cost is time in transit — the same 70-kilometre crossing each way in one day — and a limited number of dives for that effort. Divers pay the park entry fee plus a supplement widely applied at 200 baht per diver per day.
Why liveaboards exist here
Because nobody can sleep on the islands, the liveaboard is not a luxury option but the only way to be in the archipelago at dawn. Boats depart Thap Lamu, moor offshore overnight, and start diving early — first dive around half past six is standard. A four-day, four-night itinerary typically delivers around eleven dives, working the Similan sites, then Christmas Point, Koh Bon and Koh Tachai, then continuing north to the Surin islands and Richelieu Rock. Itineraries flex daily with weather, tides and group experience; no operator can promise a fixed site list.
Richelieu Rock is not in the Similans
This trips up a lot of people booking their first Thailand dive trip. Richelieu Rock — Thailand's most famous dive site and its most reliable whale shark encounter — sits in Mu Ko Surin National Park, roughly 18 kilometres east of Ko Surin Tai and around a hundred kilometres north of the Similans. It appears on Similan liveaboard itineraries because the boats continue north, not because it is in this park. If Richelieu is the reason you are booking, check explicitly that the itinerary includes Surin, and budget for a second national park fee.
Choosing between them
If you are not a certified diver, the choice is made: a snorkelling day trip from Khao Lak. If you dive and have a week in the region, the liveaboard is the better value per dive and the only way to see the park without crowds — the boats are at the sites before day-trip traffic arrives and after it leaves. If you dive but have a single free day, a scuba day trip works, though set expectations that you are sampling rather than covering the park. Certification, sea tolerance and available days matter far more than budget.