Swim instructor here.
Sounds like you've tried the usual. Group and individual lessons. I wonder if he's getting frustrated with himself. Does he still want to work on this?
Someone that scared needs to decide he is ready to do it, and be in control every step of the way.
Any idea what he is afraid of? Can he say? Some kids feel really stressed by the idea that water might splash on them. These are generally kids that are sensitive to sensory input and the anxiety just heightens it to the point where it's unbearable.
Does he dislike the lowered effects of gravity?
Is he afraid he will go under water?
Afraid of not being able to breathe?
Afraid of "drowning" (dying)?
If you know the specifics, you can address the specifics. And some kids have some interesting fears. I had one who was convinced the drains would pull him in if he let go. Very different from a kid who is afraid of choking.
Assuming you just have a regular pool, yes, standing in the water holding the side. Eventually move so that he's not holding on, but is leaning with his back to the edge of the pool. Get comfortable with tossing a ball back and forth and eventually move to using the toes to pick up a ring off the bottom.
The key is to help him set incremental goals so he sees his progress.
I've had some kids who worked for a long time to be comfortable walking in waist deep water (which is hard to find for a 7 year old). The good news is once these kids start to feel success, they do very well.
But most importantly, he has to decide for himself, and you can support him. A prize in celebration can help too like you tried.
Oh, and if it's sensory, if he rubs his face deeply with a towel before starting, it can make a big difference.
If you have a Kids First Swim school around you, they have warm water, or a therapy pool will also have warm water. Makes it more like a bath and is less of noxious sensory experience.
Once he is comfortable holding on to the wall and walking, I'd hold off on any lessons and get him comfortable on his own, challenging himself without pressure. He has seen what they do in lessons so he has a good idea and will likely progress on his own. And of course, if you have a baby pool or anywhere he can gain confidence, try that too!
Sorry, I don't have any better advice. I love working with frightened kids. They are all so individual and what works is so different for each.
Thanks so much for this! He is terrified of drowning, choking, not being able to see, of someone not seeing him struggling in the water. It makes me so sad when he tells me about his fears! I've had many talks with him along the lines, "Have I (or DH) ever let anything bad happen to you? We are there with you in the pool and we would never let anything bad happen to you.", etc. He trusts us, he just doesn't trust that the water can remain stable enough that someone could get to him if he needed help. (He acknowledges that tidal waves and storms don't happen in indoor pools - he's knows it's irrational - he just can't get past it!)
We would have to join a local gym to get regular access to a pool. I think it would be worth it. He could go in regularly and just hang out (and my 3 year old would enjoy it as well - no fears for her so far).
