Ships using quite some power. Specially for pomps, refigeration etc.
This will influence the power dement on the shore, behaps becomes the shore power even unstable.
Also most ships using 60 Hz grit. In my county, The Netherlands 50Hz is normal.
Then there is the diffence between the European and US voltage 220-230V and 110V.
The problem is more complex. Major issues first have to be solved.