Places to go swimming

Check out the Molitor next to Bois de Boulogne . Maybe nicer in summer but I believe they also have a winter pool. Quite a cool history to the place! It is the swimming pool featured in Life of Pi !

There is an indoor pool at Butte-aux-Cailles.

The link below to pool locations might help you. Pools are listed to the left on 3 pages. As you will see the reviews vary.

https://www.google.com/search?client=firefox-b-1-ab&q=Paris+piscine+int%C3%A9rieure&npsic=0&rflfq=1&rlha=0&rllag=48858938,2333870,4859&tbm=lcl&ved=0ahUKEwj3lq32iYjZAhVSwFkKHcHwDWEQjGoIbA&tbs=lrf:!2m1!1e2!2m1!1e3!3sIAE,lf:1,lf_ui:1&rldoc=1#rlfi=hd:;si:;mv:!1m3!1d38116.22402839437!2d2.3250367!3d48.859474150000004!2m3!1f0!2f0!3f0!3m2!1i844!2i697!4f13.1

For your own search Piscines interieur

Here's a link to a recent thread about your topic with a lot of useful information: https://community.ricksteves.com/travel-forum/france/swimming-pools-in-paris

Thank you All so much

https://www.timeout.com/paris/en/sport-and-fitness/swimming-pools-in-paris
Time Out, the venerable Paris magazine, has extensive reviews of Paris pools. North Americans sometimes express surprise at the dress code for men: No baggy surfer pants. It's briefs, and a bathing cap. Here's a quote from a blog six years ago: "You have to wear either un slip de bain (the skimpy trunks of boyhood) or un boxer (which looks like a weeny pair of cycling shorts)". Maybe things have changed since them. Everyone wears the cap. Time Out also notes one pool which has mixed evening swims where the rule is wear nothing -- except the cap.

The Molitor costs a lot of money and you must use the hotel to use the pool.
There are other municipal pools around Paris - 39 of them, in fact.

Everyone must use a bonnet and men must wear Speedos. Bring your own towel and toiletries.

Oh such a good question and I know an authority on this matter! :) She has made a project to swim in every public pool in Paris.
http://www.pret-a-voyager.com/2012/02/paris-practique-french-swimming-pools/

Are you not familiar with Swimmer's Guide? It is an incredible, extremely useful site. I have found pools in Rome, Florence, Glasgow, Durham, Zagreb, Sarajevo, Bucharest, Uxbridge, York, Milan, Varenna, Padova, &c. You get the idea.

A Google search will take you right to it.

The creator of the site informed me in a personal email exchange that the very most expensive place to swim he has found is in Paris, so you might want to learn enough about costs to seek that one out or to avoid it as suits your taste.

The tariff for the municipal pools is around 3 EU or 3.50 EU, if you're wondering about that.

Thank you so much everyone. Your great