One of the most enjoyable ways to spend an afternoon is a bamboo raft ride on the Yulong river in Yangshuo. There are several choices in terms of how long a ride you wish to take and where you want to finish. The longest ride is 20km from the Dragon Bridge to Gongnong Bridge which takes over 4 hours depending on the current. There are shorter rides of just an hour or so that finish at the Yangshuo Mountain Retreat. For more information on bamboo rafting, see detailed descriptions here.