Waterbending more commonly known as wet stuffbending is one of the four bending arts. Wet stuffbending is a scared art of the indians and it allows them to control that wet stuff people tend to drown in.
Notable wetstuffbenders include Sifu Katara. She would later go on to wetstuffbend blood, but was too high and mighty to use that as an awesome attack. However, Sokka has notably stopped bothering her after that discovery. Season three is expected to feature 63% more pee-bending than we've seen thus far.