The Biri Rock Formations
Six great slabs of layered rock on a Northern Samar island, hammered by Pacific swell and pooled with tidal flats at low water.
Updated 4 September 2026

AI illustration
Biri sits at the northern end of Samar where the San Bernardino Strait opens onto the Pacific, and the swell that comes through has stripped the island's north shore down to bare layered rock. Six formations are named - Magasang, Magsapad, Bel-at, Caranas, Puhunan and Macadlaw - and they are enormous flat-topped slabs and stacks, tilted and grooved, with the sea breaking hard against their seaward edges. At low tide the rock platforms between them drain into pools you can walk out across and swim in. The scale is the thing: people standing on the tops of the slabs look very small, and the noise from the Pacific side is constant.
Highlights
- Magasang and Magsapad - the two largest slabs, climbed for the view along the whole formation line.
- The tidal pools - natural pools on the rock platforms, swimmable only around low water.
- The Pacific side - swell breaking hard against the seaward faces of the rock.
- The layered rock - tilted sedimentary bedding exposed across the tops and edges of the slabs.
When to go
March to June is the calm window for the crossing from Lavezares and the safest for walking on wet rock. Time the visit around low tide, when the pools are open and the platforms walkable. From late in the year the northeast monsoon and typhoon swell make the north shore dangerous and the boats unreliable.
Before you go
Getting to Biri takes real effort from anywhere - Samar is a long drive and the boat is small and open. There is no shade on the rock at all and the surface radiates heat by mid-morning. The stone is sharp and slippery where wet, and the swell side is genuinely dangerous, not photogenic. Accommodation on the island is basic and food options are few.
Nearby
The San Juanico Bridge and Samar's northern coast, with Calbayog to the south.
What to pack for The Biri Rock Formations
Chosen from what this place is for. Tap a kit for the full checklist.
- Broken-in walking shoes or boots - Grip and ankle support matter more than looks; never hike in brand-new boots. Find on Amazon
- Spare batteries + cards - Cold and long shoots drain power; never run out at the good light. Find on Amazon
- Strong insect repellent - DEET or picaridin; the jungle is where bites and disease risk are highest. Find on Amazon
- Layers + a waterproof shell - Mountain weather turns fast; a packable rain jacket saves the day. Find on Amazon
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