I had never been in one at this age- I learnt to swim in the sea. Very cold and often choppy, but I've always hated chlorine and the whole hemmed-in artificial swimming pool experience.
I've still taken my children, but would never judge anyone on this. Hey, there must be other families where it would be considered neglectful if a child had never ridden a horse, or sailed a boat (that would be my family), or stood on a pair of skis or learnt map-reading or whatever. My dd at 11 can't ride a bike (motor skills problems).
The important thing is that the child gets to do something- but I don't think it's tremendously important what you do.
And especially, I don't think it's important at what age you start. I spent all my summers on an island, 5 minutes from the beach, and I still didn't learn to swim until I was about 6 or 7. I am a very strong confident swimmer. I know several people who have learnt as adults.
Anyway, at my dc's school, children are offered swimming lessons if they can't swim by Yr 4, so maybe the same will happen to the child in the OP.