Seikan Tunnel: 54 KM Under the Sea — Japan's 24-Year War With the Ocean

53.85 kilometers of tunnel. 23.3 of them under the sea. 240 meters below the waves of one of the roughest straits in Japan. This is the story of how the Seikan Tunnel was built, and why it took 24 years. It began with a disaster. On 26 September 1954, a typhoon sank the ferry Toya Maru in the Tsugaru Strait, and 1,159 people died. Japan decided the crossing between Honshu and Hokkaido could never again depend on the weather. The answer was a railway tunnel under the seabed. In this video, we break down how engineers fought soft volcanic rock, repeated seawater floods and decades of work in the dark, how they sealed the rock ahead of every metre, and how the tunnel finally opened in 1988. Today, Shinkansen bullet trains run through it. 🔔 Subscribe for more deep dives into the greatest engineering achievements on Earth — every week, a new impossible structure. Timestamps: 00:00 The disaster that started it all 0:23 Crossing one of Japan's roughest straits 1:10 Rock that should not hold a tunnel 2:00 Digging begins, 1964 2:51 The sea strikes back 4:10 The 1976 flood that nearly ended it 4:55 Why not a bridge, why not a plane 6:25 The fix: three tunnels, not one 8:11 Breakthrough 9:35 Opening day, 1988 10:12 Stations built beneath the ocean 11:21 The bullet train finally arrives, 2016 12:53 Riding through the tunnel 14:14 What the tunnel carries today #Engineering #Megaprojects #Japan #SeikanTunnel #Impossibuilt