How do you make pants into a flotation device?

Tie a knot in each leg near the cuff. Zip the zipper and button the button. Hold the pants by the waist band. Get into the water up to about your belly. Then swing the pants over your head and slap the open waist band down hard on the water. This will cause air to be forced into the tied off legs and make a "V" shaped flotation device that you can actually ride.