I have been taking my 4 month old weekly since he was 10 weeks. We go to council run schemes, and they cost a couple of £. You pay as you go.
Why? Well, I wanted him to be in a session without toddlers or older children splashing him before he was confident in water.
I wanted him to have some structure to his week, and we have a couple of groups, and swimming is one of them. All the classes are for his benefit not mine. We do baby sensory - that does not benefit me. Baby bubbles and rhyme, which is an hour of singing and action rhymes. No benefit for me. And swimtots. Again, no benefit to me.
He loves going to the groups and gets excited at the activities.
When we started at swimming, he cried. The water was cold for him. I bought him a neoprene wrap, and he was a lot happier. Each week he has grown in confidence, and as long as he is warm, he is happy! I can safely dunk him under water (I did this myself, not as part of the session) to get him used to the sensation of being under water. He does not cry now when he gets splashed, or water on his face/in his eyes. In fact, we have just been away to Switzerland, and went to an aquapark there. He had a lovely time, and happily went in the water, which was cooler than he was used to. He loved the lazy river, and I took him down the little baby slides.
So for me, I can see the benefit for him. It isn't about learning to swim, it is about having fun.
If he isn't having fun, we stop. Simple as that.