[en] We address the question of the composition and spatial distribution of water group plasma in the magnetosphere of Saturn. We suggest that the problem of the coexistence of neutral atomic hydrogen and such a plasma can be resolved if the dominant ion is taken to be H₂O⁺ or H₃O⁺. We also suggest that this ion may provide a means of radiative cooling of the inner magnetosphere plasma which is possibly easier to realize than transport of nitrogen from Titan. As a source for this plasma in the region inward of the icy satellites, we suggest the ring atmosphere. The depleted plasma density in the domain between the Dione-Tethys torus and the ring plane crossing of Voyager may provide an explanation for the survival of the E-ring. Data are presented which indicate that H₂O⁺ or H₃O⁺ is also a favoured candidate in the outer magnetosphere and that it can diffuse without loss through the hot electron gas