Is swimming an option in the waters of the Karoo?

I am a fan of the show and an avid camper, but not survivalist by any measure. Watching the new season I don't recall seeing anyone cooling off by taking a dip in the river, yet. (Maybe not going underwater to avoid ingestion.) Seems clothing would dry pretty quickly if hung out in the sun. What would be the reasons not to - even if only for a quick soak?