A powerful crane vessel pieces together an oil rig in the world's busiest harbor, digging a tunnel linking two countries requires chewing through rock beneath a peaceful seaside village, and armored heavy haulers remove lethal slag from a smelting plant.

Super-tugs are the sole vessels preventing disaster between massive oil tankers and unspoiled Alaskan wilderness, a heavy-lift crane has to build itself before getting to work, and only one shovel is tough enough to dig in a Chilean copper mine.