I don't have time right now to read all 23 comments, BUT, my dd was just like yours. We used to take her to baby classes. She did great. But then due to work and we moved further from the pool, we didn't go as often. Sometimes after she turned 2 she became afraid of the pool. She'd go up to her knee but that's about it. She'd scream as if we're beating her if we took her in any deeper. We kept trying and trying, just family swims, but no results. We did the bribery, we got her all sorts of goggles (hoping one would be better than the other), etc and nothing.
Sometimes last year, I think it was soon after she turned 7 (year 2), we had a talk. Her fear of water was getting ridiculous and I seriously thought of taking her in to see somebody. From the talk we made a deal. We agreed to give swimming a really good try. I told her I'd get her a private teacher and to try to be brave. Dd agreed for a few reasons. She hated her fear. She was crying and upset for being so scared of water. She also wanted to learn because in a year there will be swimming at her school and she didn't want to be that one person who couldn't even get into the pool.
Just a background on the teacher... I asked everybody I knew, locally, who is really good with kids. I got a few referrals and decided on one after we emailed back and forth a few times with questions and answers.
Whether the teacher was good or dd was just determine to get over her fear but she did it. We went private a couple of times and the teacher and I decided that dd was ready, and will be fine, going into a group swimming lesson.
A year and a half later dd is in level 5 (out of 7 here). She went through level 1 and 2 in about a term time each, level 3 took longer, I think it was 2 terms. Level 4 was the first time in the deep pool and I thought she was going to sink but she did well and 1.5 term later she got moved up to level 5. She hasn't been moved up to level 6 yet. Move up time was two weeks ago. Who knows when she'll go up, maybe the next term payment but I think she's doing marvellously well for somebody who had water phobia.
Good luck to you! I hope yours will one day be ok too!!