I've been a professional artist- basically a figurative one - and teacher one way or another all my life (see my profile), but I think the idea of 'nudism' in art is an awkward one. I can't think of many works which depict that specific activity. 'The nude' in art is of course a huge topic, but quite a separate one.

I quite agree that a painting of Bathsheba or of Salome is not "nudist art", even if it does depict the nude human body.
But wouldn't you say that the numerous paintings showing people engaged in what we would consider naturist activities, enjoying life in the nude in the open air, swimming, taking the sun or playing in the open, could be described as "nudist art"?
I have in mind works by Cézanne (Baigneurs, Les 5 baigneurs, Le repos des baigneurs, Baigneur et baigneuse, Les grandes baigneuses, etc.), Degas (Deux baigneuses sur l'herbe), Renoir (Baigneuse nue assise, Les grandes baigneuses), Matisse (Les baigneurs avec une tortue, La danse) or Kirchner (Spielende nackte Menschen, Zwei nackte Frauen  im Wald, Nackte Frauen mit Kindern, Badende, etc.).

I understand your point, Jaques, but I would argue that the context of those works was more a reference to classical mythology than a contemporary notion of 'nudism'. 'Bathers' as subject was a popular theme, as you've indicated, and of course today we might call it 'naturism', but I doubt that it was thought of in those terms by artists who were thinking more about formal ways of depicting the nude or an idealised landscape, or, in the case of Manet's La Déjeuner sur l'herbe, to shock.

Isn't the concept of 'naturism' or 'nudism' a fairly recent one, even if people have shed their clothes in the company of others since they started putting them on in the first place?

Can't see the wood for the trees. Think getting bogged down in semantics. Philosophical arguments are one aspect that can be discussed, but it can be also rich about the beauty of the body as well as personal experiences.