It's a nice mix of freeway runoff and sewer overflow packed with motor oil, body fluids, body parts, rat feces and other natural elements found commonly in natural waterways. It's a fine outing for any city-dweller who wants to experience that "back to nature" feeling.
Yeah I know, have seen it many times. I live in Bakersfield so have spent a fair amount of my life in LA for one reason or another. lol