Nonsense!
We have become totally obsessed with germs in this country...if Lysol had its way, we'd not only be spraying everything in sight with it, we'd be spraying each other with it! We can't stand the natural aromas of the human body, so we wash with "antibacterial" soap and saturate every orifice, nook a cranny with products that completely destroy them. If we keep it up, the human race won't have any immune system left--'cuz nobody will ever be exposed to the things that create antibodies. You've been swimming all your life...it hasn't killed you--or even made you sick--yet. So have I, and I'm a lot older than you are. However--dishes aren't the human body...they don't develop antibodies, but they can become "petrie dishes" while stored in the warm summer heat. So, while what they can grow prob'ly won't hurt you, it's a good idea to be a little bit careful about what you wash 'em in. So be careful to get the dishes clean, but when it comes to swimming, just pay attention to any published warnings that an area has been closed to swimming and avoid that area. Otherwise, just relax and continue to enjoy your life--and that includes swimming in your favorite coves.