We had a swimming lesson disaster this spring as well. It wasn't as bad as your stories, but the water was SO cold that both kids were blue within five minutes. We were in the water with them and I was freezing as well. We only went that one time and never went back.
We are either at a lake or my IL's pool every weekend and sometimes during the week. 4th of july weekend, Macie would still barely get in the lake and was panicked, holding on to me, etc. I kept working with her, and as of this week, she is swimming back and forth across the pool (wearing her puddle jumper) and jumping off the top step of the stairs, even going under a little. I'm so proud of her! We are going to the lake again tomorrow and probably sunday too. Asher loves the water, but hasn't figured out how to keep himself upright while wearing his vest so he keeps faceplanting. I just hold on to him or let him keep jumping into my arms.
With the hot weather we've been having, the lakes are like 80 and I'm pretty sure the pool was close to 90.