Many activities can be done in and on rivers, including kayaking, rafting, and swimming. (TNG: "Transfigurations"; ENT: "The Catwalk") A number of aquatic creatures can be found in rivers, including fish, eels, and even turtles.
Some known rivers include Argus River on the planet Rigel IV, and the Thames and Kabul Rivers on Earth. They are often the location of borders between countries or provinces, such as the Glyrhond River on Bajor between the Paqu and Navot villages (DS9: "The Storyteller") or part of gardens such as in the Bajoran monastery gardens. (DS9: "In the Hands of the Prophets")