Desert cooling

There once was a "smart guy," a "not that smart guy," and an all round "not smart at all guy." They were going to cross the Sahara Desert.

The "smart guy" says, "meet here in an hour with something useful to cross the desert with!"

Later on an hour passes. The "smart guy" says I brought some ice packs to keep our heads cool, the "not so smart guy" says I brought a pail of water to keep us hydrated.

The "not smart at all guy" says, "I brought a car door so I can roll the window down when it gets hot!"