Square Waves is a cross sea phenomenon in the waters between Kunqiu Beach and Snake Island on West Juguang Island in Matsu, where two wave systems traveling in different directions meet at high tide to form a grid-like pattern — a rare oceanic phenomenon seen in only a handful of places worldwide.
The Square Waves phenomenon occurs because of the local topography and currents between Kunqiu Beach and Snake Island: at high tide, two wave systems traveling at right angles to each other intersect to form a checkerboard-like pattern, known in physics as a "cross sea." Similar phenomena worldwide have so far been documented only at France's Île de Ré, Kunqiu Beach on West Juguang, and the Shanwei coast of Linyuan District in Kaohsiung. Research from the European Space Agency indicates that such square wave patterns conceal powerful currents and have contributed to multiple shipwrecks over the years — visitors are advised to observe from land rather than entering the water.
Highlights of Square Waves
"Square waves" are formed when two wave systems traveling in different directions intersect on the sea surface, creating a near-right-angle grid pattern under specific conditions — known in physics as a "cross sea." This phenomenon requires wind direction, tidal currents, and underwater topography to align simultaneously and is not common worldwide. Kunqiu Beach, because its bay orientation and underwater topography happen to be suitable, occasionally produces this phenomenon. It cannot be guaranteed on any given visit.
Even without the square wave pattern, Kunqiu Beach is worth a visit. Its fine white sand, clear water, and open bay shape make it one of the better beaches among Matsu's islands. The broad intertidal zone exposed at low tide hosts various shellfish and benthic organisms — a good site for nature observation. The beach is flanked by low shrub-covered hills, and West Juguang Island is unhurried and relatively uncrowded.
How to Make the Most of Your Visit
Practical Information
Getting There and Time Needed
- To reach West Juguang, take a ferry from Fuao Harbor on Nangan, approximately 1 to 2 hours; you can also take a boat from East Juguang to West Juguang. Schedules are affected by weather — check the latest information with Matsu Shipping Company.
- Kunqiu Beach is on the northern side of West Juguang, about a 10-minute scooter ride from Qingfan Harbor (West Juguang's main pier). Scooters are available to rent on the island.
Nearby Connections
- Can be combined with Caipu'ao Geopark for a West Juguang day trip — the two sites offer contrasting geological landscapes.
- There are ferries between West Juguang and East Juguang. Consider a two-day plan: one day each for East Juguang (lighthouse, Fuzheng Village) and West Juguang.
Source: Matsu National Scenic Area Administration, Lienchiang County Government tourism information. Photos pending Dio's on-site shots.
Frequently Asked Questions
How does the Square Waves phenomenon form?
At high tide, two wave systems moving at right angles meet in the waters between Kunqiu Beach and Snake Island, creating a checkerboard pattern known as a cross sea.
Is Square Waves a globally rare phenomenon?
Yes — similar phenomena have so far been documented only at France's Île de Ré, Kunqiu Beach on West Juguang, and the Shanwei coast in Linyuan, Kaohsiung.
What should visitors keep in mind when viewing Square Waves?
European Space Agency research links such square wave patterns to powerful hidden currents and past shipwrecks, so visitors are advised to observe from land and avoid entering the water.
Sources
- 方塊海－連江縣海洋資源中心 — 確認成因、最佳觀察潮汐時機
- 世界級海洋奇景「方塊海」專家建議陸地上欣賞即可－馬祖日報 — 確認全球稀有分布地點與觀賞安全建議