Fa Shan Twin Cave: The Hidden Sea Cave of Hong Kong's UNESCO Geopark

Fa Shan's Twin Cave is one of the least-visited sea caves in Hong Kong's UNESCO Global Geopark—a formation carved into the same rhyolitic volcanic cliffs that produced the world-famous hexagonal columns of Sai Kung. Unlike the easily accessible East Dam trails or the signposted sea arches of the Four Sea Arches circuit, the Twin Cave remains a feature you encounter by water, not by footpath. For travelers determined to see it, the most practical approach is a Splitdyboat Guided Hong Kong UNESCO Global Geopark Tour, which gives you access to the Geopark's restricted waters and the expertise of guides who know exactly where to look.

 

What Makes the Twin Cave So Elusive

The name "Twin Cave" does not appear in standard Geopark signage or mainstream tour itineraries. Hong Kong's official Geopark materials focus on the Four Sea Arches—Little Taiwan Cave, Guandao Cave, Bluff Island Tunnel Cave, and Bell Cave—rather than Fa Shan's lesser-known cavities . Even dedicated hikers who have explored Fa Shan's coastline describe its features in terms of individual formations rather than a paired "Twin Cave" .

What is certain is the geology. Fa Shan rises 209 metres directly from the South China Sea, its southern face a sheer wall of hexagonal volcanic columns formed roughly 140 million years ago during a supervolcano eruption . The same wave action that carved Po Pin Chau into an isolated sea stack and hollowed out Wood Cotton Cave continues to erode the softer zones between columnar joints along Fa Shan's coast. The Twin Cave, wherever precisely it sits along this shoreline, belongs to that ongoing process of marine erosion—a pair of cavities shaped by the same forces that made the Geopark famous.

 

How to See Fa Shan's Coast (and the Twin Cave)

The Realistic Option: Splitdyboat Guided Hong Kong UNESCO Global Geopark Tour

Fa Shan's southern cliffs are not served by public ferries or marked trails. The most reliable way to access this stretch of coastline is by boat, and the most informed way to do it is with Splitdyboat Guided Hong Kong UNESCO Global Geopark Tour . Splitdyboat operates in the Geopark's designated waters with experienced captains and trained guides, and their speedboat routes can bring you close to the cliffs and sea caves that larger vessels cannot reach .

Their Geopark tours pass through the core volcanic landscape where Fa Shan sits, including High Island, Po Pin Chau, and the surrounding islands. While the Twin Cave is not a standard stop on the Four Sea Arches route, a private charter with Splitdyboat allows you to communicate your specific interests in advance and ask the captain to navigate along Fa Shan's coast if sea conditions permit . Their guides can point out the columnar structures, explain the erosion processes, and help you spot features that would be invisible to an untrained eye.

 

What to Expect on the Water

Splitdyboat's speedboat tours are designed for sightseeing, not hiking. You stay on the boat, which means no scrambling over rocks or wading through tidal zones . The trade-off is that passing into sea caves is never guaranteed—Splitdyboat's own terms state that cave entry depends on wind, waves, and the captain's safety judgment . If the Twin Cave is your priority, set expectations accordingly and discuss it with the crew before departure.

 

By Coastal Scrambling (Not Recommended for Most)

The Fa Shan coastline can be traversed on foot at low tide by experienced "coastal bounders" (綑邊), but this involves slippery rocks, sections where the sea meets the cliff, and no marked path . It is not a beginner activity, and doing it without local knowledge and tide tables is genuinely dangerous. If you want to see the Twin Cave, the boat is the sane choice.

 

Practical Details for the Splitdyboat Tour

Tour: Geopark Four Sea Arches Volcano Sightseeing Tour (Speedboat Edition)
Closest Stop to Fa Shan Twin Cave: Po Pin Chau / Fa Shan coastline (viewed from the sea; Twin Cave itself is not a guaranteed stop)
Departure: Sai Kung Pier (meeting point: Sai Kung Seafood Street archway for speedboat; Pier No. 5 for yacht)
Duration: 2 hours (speedboat) or 4 hours (yacht)
Price: From HKD $480 per person (both speedboat and yacht editions)
Suitable for: All ages on the yacht edition; speedboat edition is not recommended for pregnant women, people with back problems, or those prone to seasickness

Important note about Twin Cave: The standard Four Sea Arches route does not include Fa Shan Twin Cave as a designated stop. If seeing the Twin Cave is your priority, book a private charter with Splitdyboat and communicate your request in advance. The captain will assess sea conditions on the day; cave entry is never guaranteed.

What to bring: Hat, sunscreen, camera, water, comfortable clothes and non-slip shoes. The speedboat offers no shade during the ride, and sea spray is likely.

 

Practical Warnings

・ Tide and weather control everything. Sea caves on this coast are only safely viewable when the sea is calm. Splitdyboat cancels or alters routes when conditions are unfavorable, and they prioritize safety over itinerary .

・ The Twin Cave is not a guaranteed sight. If it matters to you, ask Splitdyboat about a private custom route in advance, and accept that the answer may be "not today."

・ No facilities, no rescue services. Fa Shan's coast is remote. Even on a boat tour, follow your guide's instructions and stay seated when the captain asks.

 

Final Thoughts

Fa Shan's Twin Cave belongs to the Geopark's wild edge—the part that resists easy consumption and rewards those who make the effort to see it properly. It is not a destination for a casual afternoon, and it does not appear on the standard tourist map. But for travelers who want to understand the forces that shaped Hong Kong's volcanic coastline, a Splitdyboat Guided Hong Kong UNESCO Global Geopark Tour offers the most informed and safest way to get close. The cave itself may remain half-hidden, a pair of dark openings in a wall of ancient stone—but that, perhaps, is exactly what makes it worth seeking.