Prevent underwater camera fogging

Just a tip I read over on wetpixel, you can cut down on fogging by putting your camera in its housing in a cool, dry environment (like an air conditioned hotel room at night) and keeping it covered or out of the sun in the day. From what I read, it seems like the greater the temperature difference between your camera/housing and the water (or is it the air and the water) the more fogging you might have.