How to make an emergency life preserver
If you don't have a plastic bottle, gas tank, styrofoam cooler, or other similar item, you can make a floatation device from a pair of pants.
1. While treading water, take off your pants and make a knot in the end of each leg to close them off.
2. Lift the pants out of the water with the waist facing down. Use a downward motion to fill the legs with air.
3. Place yourself between the legs and use them to help you float. If the air escapes from the legs, repeat step 2.