I breastfed all 3 of mine (in the last decade), and took them swimming every Sunday. Our local baths has a 'beach pool' for younger kids, so I could watch the older ones in the water, whilst I fed the baby on the loungers (using a towel to cover my cozzie, partly to make sure nothing was on show, but to also stop me getting cold) or sitting on the edge with my feet in the water (which kept me warmer: the beach pool was more the temperature of bath water!).
The kids loved the water, and wanted to spend more than an hour at the pool - too long for the baby, so once she'd had enough, I fed her and then she slept in the car seat at the poolside whilst the older 1 (or later, 2) could splash for a little while longer. No-one ever complained, some mums even gave me a nod & smile, as I was the first to do it, but then it became more common among other mums.