Mahouts (elephant handlers) often take their elephants down to the Rapti river on the Sauraha side in the evenings for a bath. In the background a local fisherman comes back.
There are local tables and chairs where you can order drinks/meals and to watch the sunset over the jungle and river. At the same time you might be lucky enough to see an elephant bath for free - though you can offer a small tip.
There are regular dedicated elephant bathing sessions in Sauraha during the day. These are paid for packages. The photograph above is a more natural realistic elephant bath. Do read my full guide to Chitwan National Park for more or view the large Chitwan map find out where this is.