Sent home to her father, Tui then rides her horse down to an encampment of women who live bythelake, led by their mentor-cum-oracle called GJ (Holly Hunter).
The key was not to try to dig a Suez-type of canal, a great sea-level trench from ocean to ocean, but to create a lock-and-lake canal, where the ships are lifted up by a series of locks to a man-made lake, and then they sail across that lake, and then they are set back down on the other side by another series of locks.
Martin Siegert points out that the water in the drill head will only be a few degrees above 0C as it enters thelake - it inevitably cools as it flows 3km down into a hole that is surrounded by ice at -35C.