My ds wouldn't even get in a pool until he was 5. At first, all he would do was ride around the pool on his dad's back. It took him years to be comfortable enough for lessons.
His 3rd grade teacher taught swimming lessons at her home in the summertime, so I arranged individual lessons for him. He did so-so until he found his sister's snorkel mask. With the mask covering his eyes and nose he felt safer and he quickly learned how to swim!
He wore a snorkel mask every time he swam until he hit his teens!