While in Koh Lanta, take the four-island expedition. These excursions take you to Koh Chuak, Koh Kradan, Koh Mook and Koh Ngai. You can find full-day treks to the islands as well as the surrounding caves, which are typically priced at around $50 per adult. You get to swim along a heart-stopping pitch-dark 80-metre narrow passage with the assistance of a tour guide and your flashlight. Once you go through it, a hidden lagoon, surrounded by towering limestone ridges, will be there to greet you! It is an experience you won't be forgetting anytime soon. Apart from these activities, usually, a tour comprises a hotel transfer, potable water, a lunch buffet, snorkelling gear, and the fees for the National Park. Check online for more details and bookings!