My dd takes lessons at AquaKids in Flower Mound which is great but a little far for you. I would check out Emler in Plano, it may be a little distance but every kid I know who has taken at Emler or AquaKids actually learns to swim, not just "be comfortable in the water". We obviously still watch her but after 2 sessions as a 3 year old, it was so nice to be able to play in the water with her rather than have to carry her or a float thing around.
Both places have indoor pools so they do lessons year 'round.
Good Luck!