I don't think it's hand wavey. It's just a different (simpler) model. To describe this phenomena (wet things are darker), you don't need to go into details abou

I don't think it's hand wavey. It's just a different (simpler) model. To describe this phenomena (wet things are darker), you don't need to go into details about photons, or quantum mechanics or whatever. Geometrical optics is really sufficient here, it explains it perfectly, and is much more intuitive than other more complex models.