What safety risks exist that do not exist for other forms of fuel and energy?? Wouldn't marine be the perfect use of hydrogen? The only output is water. Energy storage of hydrogen is cheaper by weight then battery. If there are some solar panels and/or wind generators on part of the vessel then couldn't it technically stay adrift from shore forever (temporarily forget food for humans or degradation of the boat without maintenance).
Liquid fuels are generally less flammable, and minor leaks don't present a serious problem. Batteries will never have the capacity needed by long distance merchant ships. Fuel weight isn't very relevant, it's tankage volume that matters more. Ships don't have enough free surface area to generate much useful power from solar panels. Wind generators are counterproductive if you actually want to go anywhere because the extra drag exceeds any power they generate.
Long term I expect we'll primarily use nuclear and renewable power plants on shore to drive manufacturing of synthetic liquid hydrocarbon fuels for marine and aviation markets. That appears to be the safest option and won't require rebuilding entire major industries.
