"It's impossible to train yourself to function without much water," says Kenneth Kamler, M.D., noted Everest expedition doctor and author of Surviving the Extremes. The general logic behind your theory does have some basis in fact, though. Adventure travelers have long known that physical conditioning for a trip can go beyond just getting one's muscles into shape. As you mention, early polar explorers prepared themselves for subzero temperatures by taking frigid showers. And some present-day adventurers, like Norwegian explorer Børge Ousland, take a more extreme approach: In preparation for a North Pole expedition in 1990, Ousland spent a month sleeping outside in Canada's far north. "If your training is too controlled," Ousland says, "you will not be prepared for the physical and mental stretching that happens on expeditions." Kamler notes that scientists have an idea why this type of conditioning might be effective: "When your body is stressed it creates something called chaperone proteins, molecules that protect regular proteins from being damaged in extreme situations." Do these protein-building stresses include, say, dehydration? Yes, Kamler says. Starvation, dehydration, and extreme heat or cold can all increase chaperone-protein levels. But so can good old-fashioned physical exercise. Purposeful deprivation of food and water should not be part of any training regimen, says Kamler. So drink up!