Hi, can I add my 2c?
Back in the day to support my studies, I used to teach swimming to mainly 3-5 year olds.
My speciality (if you can call it that) was with the traumatised kiddies.. most of whom had been naturally reluctant of water and been pushed beyond their comfort levels too soon.
With these kids it took me 5 times as long (or longer) to get them to the same level as the confident ones.
One 12 year old girl took 6 months just to progress to walking through the water, such was the extent of her terror.
I understand the desire to get kids swimming early, given all the pools/sea etc that they've access to, but I want to stress that no young child is ever really safe near water. pushing too hard too early and you stand a real chance of putting your child off for perhaps years. water play should be fun and enjoyable... if it isnt, you're just setting yourself up for an extended period of required lessons... with a real possibility that nothing will be learnt and you'll just have to start all over again in a year or two. Obviously, some kids take to the water like fish though too.
My husband has been taking my son to swimming lessons since he was ~9 months for two reasons primarily... because it was something fun for them both to bond over (dad-Ben time

) and because a love for the water is something I wanted my boy to develop. Our swimming lady is lovely. Parents are in the water with their children and the focus is very much on exploration and fun. I'd definitely not be taking Ben there if the focus was trying to 'drown proof' the kids... because sadly, this just isnt possible for most.
so my advice would be to take the cue from your child. if they're resisting and it just doesnt feel right, give it a break for a few months, or try a teacher with a different approach. Swimming can and should be a life-time enjoyable activity.