Anonymous wrote:You need to tell the head coach. And please do. I have 2 young sons and this would disturb me as well.
When you talk to the head coach, you can come at it from the perspective of, "We are being very solid with DS about this messaging, that he's not to go near someone's private area, and I don't want the issue being confusing for him if he thinks it's okay sometimes and not other times. Nobody should be going near his private area and he shouldn't be needing to touch someone else's either. Certainly not people from his swim team or his coaches." etc etc. And you should also make it clear that you'd be willing to leave over this, and also that you've discussed it with other moms who have agreed that they would not like it either. Don't let them downplay your concerns.
P.S. I would also say, from what you wrote, that my guess is that the boy is socially awkward in general, doesn't relate to people well or have many friends, and that this is the reason the mom in particular is jumping on the chance to have a "friend" for the boy to have a playdate with. So I'd try to have a bit of compassion when talking to people about it, but yeah, it's definitely inappropriate.