It may be the easier option for electrically propelled ships, several of which are already in service. Mind I'm not talking about battery-electric ships but diesel-electric (hybrid, [1]) which have the range and load capacity needed for 'serious' applications. If - and that is a big if - the requisite fuel cells can be developed they could directly drive the existing electric propulsion units in those ships, replacing the diesel generators currently in use.

[1] https://www.wartsila.com/marine/products/ship-electrificatio...