Andy getting a shower from a waterfall. He has clipped his backpack to a his harness at let it hang at his feet - this technique is helpful on long or awkward rappels where, if you have a heavy pack on your back, physics dictates that the backpack will try to flip you upside down, and you will have to struggle to remain upright. Hanging your pack keeps you upright and also allows you more maneuverability especially in confined chimneys and waterfalls.