Eiksund Tunnel - World's Deepest (video)

Continuing the world records, today a visit to the deepest undersea tunnel at −287 metres (−942 ft), and length 7,765 metres (25,476 ft). See the short video, as you enter and exit there are blue lines on the walls, which I assume represent the waterline (not sure if it's the surface or the bottom, the bottom would make more sense). It also has a cavern in the middle.