I think we have to look at all sides, HIV is carried in breast milk. That's a fact, and boobs squirt when a baby latches on, also a fact.
My boob squirts were extremely forceful, and I was amazed when i let down I could get my milk so far across the room with my babe on the other one.
Re HIV, Lets just say hypothetically, that the lady didn't give birth in a country where she is legally obliged to take a HIV test when pregnant, or she has successfully contested the hospital's decision to mandatorily test every pregnant woman. Or she only showed up in the hospital to give birth whilst her baby was crowning, and avoided all prenatal care- something that happens a lot where I live. (About 10% of one particular hospital births, and mostly of Nigerian women iirc from discussions with consultant obs)
Then potentially a mother could have HIV virus in her breast milk. Milk does squirt out when a baby feeds, and also milk covers the baby's little face when s/he feeds.
There is a potential chance that HIV virus could hit someone's open wound, especially as people are wearing their togs, and have more skin exposed. There is a chance, maybe a slim one, but a chance none the less.
The risk of transmission is there, even if its small. You can't ignore that risk, just because you post a bit on the internet and think of yourself as being urbane and clever.
Now, otoh, I'm all for bf mother's rights to parent their babies as they see best, and I also know having bf in public how horrible it is to have people get their judgy pants in a twist because they view your boobs as something other than the way you and your baby sees them, and move you on for being disgusting or an exhibitionist.
But, I think a swimming pool has a no food or drink policy, so that rule is the one I think must be adhered to in this case.