Stop by the Chicago River on a summer day, and you'll find plenty of kayakers, architectural cruise boats, and people snapping photos and making memories. But swimming, let alone organized swimming in the Main Branch of the Chicago River downtown is not a common sight.

As many as 500 swimmers are expected to dive into the Chicago River next month as part of a fundraiser for ALS research and youth education programs.

Before hundreds of swimmers are set to jump into the Chicago River in September, organizers and advocates say they are taking a “victory lap” of their own. On Thursday, the city of Chicago approved the first official open-water swim to take place in its urban waterway in almost a century.