Can humans die if you swim in polluted waters?

Yes. It does, of course, depend on exactly what the pollution is and whether you swallow any of it or not. Technically, any lake a motorboat has been on is "polluted", since it will contain traces of oil, but you can probably swim in that with no problems.
Yes. It does, of course, depend on exactly what the pollution is and whether you swallow any of it or not. Technically, any lake a motorboat has been on is "polluted", since it will contain traces of oil, but you can probably swim in that with no problems.