Koh Phanak features a sea cave known as Tham Lot, which was formed by the erosive power of waves, creating a tunnel-like passage into the cave. Inside, you will find stunning stalactites and stalagmites. To explore the interior of the cave, you need to paddle a small canoe gently through the darkness during low tide, until you emerge on the other side into a shimmering emerald lagoon surrounded by towering cliffs.