I would avoid it, but thinking back to all the cruddy water (lakes, ponds, canals, etc) I swam in as a kid, taking in gulps of water while playing and goofing around, I never got sick from any of it. But I remember that drinking well water in northern Michigan would cause things to pass through rather quickly. Every summer camping, regardless of the campground, well water would clean us out pretty good.
Not sure what this means, but I would still try to avoid drinking standing water.