A river is a stream of water flowing over a riverbed in a channel and confined by riverbanks on its sides. Beginning at a higher elevation, this water flows into a lower elevation, ending at an ocean or lake.
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 or part of gardens such as in the Bajoran monastery gardens. (DS9: "The Storyteller", "In the Hands of the Prophets")
Rivers also feature prominently in religion and mythology. For example, in Klingon mythology, the River of Blood surrounds the realm of Sto-vo-kor.
The song "Row, Row, Row Your Boat" was about rowing down a river, called a stream in the song, in a rowboat. (Star Trek V: The Final Frontier)
Starfleet's Danube-class runabouts were named after rivers on Earth. (DS9: "Family Business")
When Lieutenant Malcolm Reed chased a Novan out of the forest, the two ran through a shallow river on Terra Nova. (ENT: "Terra Nova")
On the property bought by Benjamin Sisko in the Kendra Province in 2375, there was a river running through the land. Sisko described it as a "stream". (DS9: "Penumbra")