We did 1 term of lessons at 6 months old. But it was so incredibly boring and repetitive that we stopped going to lessons. Every single week they did the exact same thing. And this class was meant to go up to 18months old! It is a shame that this is our closest pool and has the best water treatment system in town (no chlorine). I just wish their lessons were better. The next closest pool has really high chlorine levels and only has 2 showers available.
My daughter is now 17months and I am considering putting her back into lessons but I am hesitating. She goes swimming once a week with her grandparents so she is familiar with the water. She loves it - well most of it... not water on her face. We did do the ____, ready go for months and months when my daughter was a baby. But we stopped. I wish we had continued to do that so we wouldn't have this problem now.
Maybe I will get them to watch some Uswim videos and see if we can follow some concepts from that. Also I found this blog very interesting - it is someone who details what their child did in swimming lessons over a year or more, and includes the lessons content/activities, even diagrams etc
http://www.bringemup.com/sections/Infant-Swimming