River Rush is a sub-level of Sonic Boom: Rise of Lyric. Essentially one straight water route, River Rush takes place on a river leading from the banks of Cliff's Excavation Site to the outer boundaries of The Pit. For this level, the player takes control of the Riptide.
Using Salty's Riptide, Team Sonic traveled down River Rush to find the Chaos Crystal in the Pit. Along the way, they were attacked by Dr. Eggman, but the team managed to escape.