I can't imagine any way other than to have it torn down and build a new pool.
I do have another suggestion. How about swimming lessons? Swimming is fun, a good form of excercise and, in my opinion, a critical life / self preservation skill. I know several people who have learned to swim in thier adult lives, there's no too old to learn to swim.
Does the pool have a shallow end with a rope to mark where it gets deeper?