In the very Paris of summer there are open city beaches in the center of the city on the banks of the Seine. So in hot weather in summer and in Paris you can sunbathe

And the big resorts on the Atlantic at a distance of 2 to 3 hours from Paris by train are:

• Deauville - Trouville
• Honfler
• Saint-Malo
• Dinar
• La Baule

Also at two hours drive from Paris on the road to Champagne near the city of Trouart there are lakes (Lac D'Orinet, Lac du Temple) where you can also sunbathe.