There are two competing mechanisms of water transfer between the ionomer-phase distributed in the catalyst layer and the catalyst layer pores; these are: (i) sorption/desorption and (ii) water dragged by the protons engaged in the electrochemical reaction (the secondary current). The level at which water accumulates in GDLs is determined by the saturation equilibrium at the GDL-channel interface. The level at which water accumulates in the catalyst layer is determined by the GDL permeability and the saturation equilibrium at the GDL-catalyst layer interface. In the cathode flow domain mass is overall produced by (i) mass of protons crossing the double-layer and (ii) mass of water transferred between the ionomer-phase distributed in the catalyst layer and the catalyst layer pores; for this reason the homogeneous multi-phase models based on the two-phase mixture model are inadequate to describe two-phase phenomena in PEMFCs. We propose a multi-phase, multi-fluid model that captures these phenomena.