Synchrotron X-ray radiography was utilized to study the time evolution of liquid water in an operating polymer electrolyte membrane (PEM) fuel cell. A high aspect ratio fuel cell, designed with offset anode and cathode flow field channels, was operated at conditions that produced critical water management issues. The X-ray beam was directed into the plane of the fuel cell, and was therefore employed to elucidate the through-plane distribution of liquid water in the porous materials. Due to the offset between the anode/cathode gas channels, the membrane electrode assembly exhibited sinusoidal warping, and liquid water accumulated in possible areas of delamination. Liquid water first appeared near the cathode catalyst layer, and then travelled laterally within the porous gas diffusion layer. Finally, future design considerations are presented, including membrane thickness and attenuation estimates.