Now I'm not endorsing swimming in the Hudson River per say but it has been cleaned up a lot and the natural life is starting to return and they did just build a beach on the island Manhattan
Okay who am I kidding, I want to jump in to the Chicago River to prove my point about it being relatively fine to swim in most urban rivers nowadays due to environmental legislation and shit. This of course does not apply to the Ohio River my sweet darling, she is polluted and sick still