We've been taking her to the pool intermittently for a few weeks and she's had a great time, and she had started asking for lessons.
And then one of her friends at nursery had some slots open up in her class, so we signed her up, and she just had an awesome time, the teacher got her to not use her water wings, and she's delighted about all of it.
(The classes have up to 4 kids in them, so it's concentrated attention, which seems to be working very well! And parents don't go in with them, so they don't get distracted.)