Riverfruit was a fruit native to the planet Alzarius in E-Space. Riverfruit resembled an Earth watermelon. It appeared to be part of the staple diet of the Alzarians, who apparently farmed it as a crop. The exterior of the riverfruit was dark green, whilst its interior was typically dark yellow.
The Alzarians considered riverfruit theft a relatively serious offence. The Outlers led by Varsh stole a number of the fruit from a pile near a river. Adric, in a bid to prove his worth, also attempted to steal some but was spotted and dropped them in his haste to escape.
Before and during Mistfall, Alzarian spider eggs appeared within riverfruit. These would rapidly develop until the fruit split open and released the adult spider. (TV: Full Circle)
While aboard the Urbankan mothership, Adric mistook an avocado for a small riverfruit. (TV: Four to Doomsday)