The issue is dealing with the salt/brine...
I guess if a ship is travelling around, it disperses it a bit more, so maybe less of an issue?
At least electrolysis & hydrogen power generation is net-positive for power generation. You know, ignoring the first law of thermodynamics (or similar conservation of energy laws). So once we solve for those, it's a home run!
Desalination equipment for drinking water on ships already discharges brine. iirc they mix it like 5 or 10 to 1 with sea water so it's not nearly as salty.