Rikkitic:I am in no way an engineer but I was thinking of an underwater tunnel anchored at a suitable depth to the sea bed (so as not to obstruct shipping). Could be constructed on the ground with segments towed into place and sunk to desired depth, then connected up and water pumped out. A lot like a space station. Many billions but many billions less than drilling a tunnel.
That's how they're doing the Fehmarn Belt link, across the shallow, flat, geologically stable Baltic. Should take around ten years to build, projected cost around EUR $10 billion, but of course it'll cost much more by the time it's done.
