Both are iconic Andaman day trips from Khao Lak — but they are very different experiences. Here is the honest comparison.

The one-sentence answer

Choose Similan for world-class snorkeling in a protected national park with near-zero crowds at the water level. Choose Phi Phi for dramatic scenery, iconic landmarks (Maya Bay, Pileh Lagoon), and the classic Andaman beach-hopping day — but expect company.

Why choose Similan

The Similan Islands sit inside Mu Ko Similan National Marine Park, which limits daily visitor numbers. Underwater visibility regularly exceeds 20 metres — often reaching 30–40 m in March and April. The reef fish, granite boulders and coral gardens are untouched in a way Phi Phi cannot match after decades of heavy visitor traffic. The islands themselves are beautiful but low-key: white sand, granite rocks to climb, and not much else above the waterline.

Similan is the right choice if snorkeling quality is your main criterion, you want relative quiet, or you want the best water in Thailand.

Why choose Phi Phi

The Phi Phi Islands day trip packs in more variety above the waterline: the limestone cliffs of Phi Phi Leh, Maya Bay, Pileh Lagoon, Viking Cave, and the viewpoint on Phi Phi Don. It is a photographer’s day. Marine life around Phi Phi is still enjoyable — reef fish, occasional sea turtles — but visibility and coral health trail the Similans.

Phi Phi is the right choice if you care as much about scenery and landmarks as snorkeling, you want to see Maya Bay, or the journey time is a factor (Phi Phi is closer).

Journey time and logistics

From Khao Lak, the Similan boat crossing from Thap Lamu pier takes 60–90 minutes each way. The Phi Phi trip involves a road transfer south to the Royal Phuket Marina first, adding travel time before the shorter speedboat crossing. Both are full-day commitments door to door.

Availability

The Similan National Park is closed mid-May to mid-October. Phi Phi runs year-round (Maya Bay closes July–August for environmental rest). If you are visiting in the green season, Phi Phi is your only option of the two.

Our recommendation

If the season is open, do both if you have two days. If you must pick one and snorkeling matters to you, pick Similan — it is one of the genuinely unmissable underwater experiences in Southeast Asia. If the season is closed, or you want landmarks over marine life, pick Phi Phi.