As Sarangel said, these are completely different cases. If the woman did not intend to swim, and other people were allowed to wear their "street clothes" into the pool area, then this is indeed discrimination. Whether it's religion based or just clothing based doesn't matter, it's still discrimination. This is a public pool, meaning that it is funded by the government and our taxes. This woman's taxes, no matter what religion she is or what religious beliefs she has, helped to fund this pool and she should not be turned away from letting her children swim. And I would guess that she and her family probably did feel pretty humiliated; imagine if you went to a public place for a family outting and were treated this way in front of your children and the general public.
To say that this is an issue of safety, that the dress would make it more difficult to rescue the woman, could be the only point the pool has going for it. However, this means that the pool should also bar all grossly overweight people, afterall, they're going to be hard to rescue, and they can bar all small children, because they're quite a risk around water. But that's not going to happen, imagine the uproar if these people were banned.
Muslim women in full dress come to the beach I work at all the time and not one has fallen into the water and drowned because of her clothing. From what I've seen, they don't come to swim, but to spend time with their families. They stay close to their children to keep an eye on them, which is more than I can say for most of the other women and families that come to our beach.
JoHare~ That's pretty harsh. To say you disagree is one thing, to say you hope someone drowns because of their religious beliefs? That's just sad.