Under pressure. (Physical/Technology).

The "Hardsuit"--also called a "Newtsuit" (after its inventor Phil Nuytten)--is a wearable submarine. The stylish machine weighs in at 227 kilograms (500 pounds), and sheathed in its aluminum hull a diver can safely descend 305 meters (1,000 feet) below the sea surface. There, water pressure, a measure of force per unit of surface area, bears down with a crushing 500 pounds per square inch (psi). "It's like having a London double-decker bus parked on top of you," says Nuytten.

At sea level, 14.7 pounds of air press down on every square inch of the body--a force equivalent to roughly 1 atmosphere. But as a diver plunges into the ocean, pressure increases by 1 atmosphere every 10 m (33 ft), and mounting pressure begins to crush the diver's lungs. Like all submarines, the Newtsuit maintains a comfy 1 atmosphere around the diver, eliminating the pressure problem.

So why does underwater explorer Robert Mester look so uncomfortable? Going head to head with a large sand tiger shark could make anyone sweat. But Mester says if the shark bit his Hardsuit, most likely "it would lose teeth, get a terrible headache, and a really bad taste in its mouth."--K. M.