Koh Bi Da Nok

Koh Bida Nok — ‘outer father’ in Thai — is the larger of two limestone islets rising from the Andaman Sea about 1.5km south of Koh Phi Phi Le, inside Koh Phi Phi’s national park. Its twin, Bida Nai (‘inner father’), sits closer to Phi Phi Leh and Don and is the more sheltered, shallower of the pair. Neither island has a beach — both are sheer limestone cliff rising straight from the water — so this is a stop you experience from the boat and the water, not on land. Entry falls under Hat Noppharat Thara-Mu Ko Phi Phi National Park’s fee: 400 THB for foreign adults, 40 THB for Thai adults, usually collected separately from the tour price.

Bida Nok’s underwater terrain varies a lot across a short distance. A sheltered bay on the south side offers calmer, shallower water reasonable for confident snorkellers, while the channel between Bida Nok and Bida Nai drops to 30 metres or more and can run a genuine current — enough that dive operators rate it as a proper scuba site, not just a snorkel stop. Reef life is dense either way: schools of yellow snapper and juvenile barracuda gather on the southwest corner, and sightings of reef octopus, hawksbill turtles and blacktip reef sharks aren’t unusual. Above water, the limestone cliffs are riddled with wind-carved pockets where seabirds nest.

Watch out: The current in the channel between the two islets can be stronger than it looks from the surface. Stay near the boat crew’s marked snorkelling zone rather than swimming out toward open water, especially if you’re not a strong swimmer.

Most visitors see Bida Nok as one stop on a longer Phi Phi day trip that also covers Maya Bay and Phi Phi Leh’s other bays, so time here tends to be brief — enough for a snorkel loop and a look at the cliffs, not a lazy afternoon. That suits the island’s character: there’s nowhere to sit once you’re off the boat, so the appeal is entirely in the water and the rock formations above it.

Insider Tip: If your boat gives you a choice, ask for time on Bida Nai’s east side instead of the main Bida Nok channel — it’s the shallower, calmer half of the pair and better suited to snorkellers without a dive background.

Combine it with Hat Maya and Koh Phi Phi Le on the same boat trip — most operators run them as one loop rather than separate excursions.