Anchor in the channel between the three islands in 12 meters being careful of the shallow water on the east side of the channel between Koh Yai and Koh Na Khae. Alternatively, anchor on the south side of Ko Hong in 4 to 5 meters close to a tunnel which has all-tide access leading to the main hong. Ko Hong has the biggest hong in Phang Nga bay. The main hong is accessible by dinghy at any state of the tide but is best visited at high tide. Leading from the west side of the main hong is a small tunnel to another two smaller hongs. You can only enter them by sea kayak at mid-tide. There is a ranger station on Ko Yai and as soon as you anchor they will approach you for National Marine park fees as it is part of Ao Phang-Nga National Park.
Be aware of the strong current in the channel between the islands.