I think it was on better homes and gardens or something similar where I saw an older couple that were over their swimming pool so they turned off all the equipment and turned it into a pond. It looked amazing. It was covered in water lilies and had an abundance of frogs which kept the mosquitos at bay. I have always said when the kids leave home that's what I'm doing to ours.
My daughters face looks a bit .The pool is watering the lawn right now and its all over.Tough decision and i bet we are in for stinking hot summers from now on .I think its destined to become an aviary.
Plenty people have gone the route of making their pool naturally filtered ponds (big enough to still swim in too if it tickles your fancy). However they are more expensive to run than a pool. Fish require lots of work too and well you need to be dedicated to it. Bonus is you already have the pumps etc and with a little tweeking and additions of UV lights you could probably have a nice pond... You got any big fishing birds there that would love to dip into your pond and steal your catch?
I vote for using a sprinkler on the lawn and running through it on hot days - brings back your youth and easily maintained.