For military needs, in early days, plenty of underground piers were built in Matsu for guerilla boats to use. Today, since the army provides the access to the piers to the public, these facilities become unique war-time sites.
Beihai Tunnel, situated by Tieban coasts, is a grid-structured waterway that goes deep into the mountains. Crossing through the rocks, it is 18 meters tall, 10 meters wide, and 640 meters long. In high tidal hours, the water goes up to 8 meters tall, and in low tidal hours, it dwindles to 4 meters low. The tourist path along the tunnel is 700 meters long. A round trip takes about 30 minutes.
Note: The tunnel is open to all visitors, but please be aware of the tidal hours before you make a visit.
A good place to watch the Blue Tears on a boat
In recent years, the tunnel has served as an ideal place for watching the Blue Tears, since the area has barely any light pollution at all. Take a rowboat into the tunnel and look for those subtle glows. What a worthy experience.
Note: Blue Tears cannot be expected but only to be encountered naturally. Do not use flashlights. Do not stand up or change seats while on the boat, just to ensure your own safety.