Swimming is of course possible in the Mediterranean see. But for those who find it too far, there is a quiet lake in Belcaire near Camurac. You can also rent pedal boats.
Axat and Ax-les-Thermes have outdoor pools who are open in the summer. In Foix, Lavelanet and Andorra are several indoor pools. Ax-les-Thermes and Allet les Bains have also thermal baths.