People familiar with the Antarctic tourism industry weren't surprised that a cruise ship sank there. What stunned them was that the ship in question was the MS Explorer, a veteran of the polar cruise ship trade, purpose-built to operate in extreme polar environments, and manned by an experienced crew. That it sank during what appears to have been the most routine of circumstances – cruising through young pack ice in mild weather – has experts scratching their heads. "I'm totally shocked and surprised," says Leif Skog, who was captain of the Explorer for six years in the mid-1980s and early...