Isolation transformers have been around for years and have been considered the best way to keep stray current form entering a vessel.
Isolation transformers work buy making new AC power from the in coming shore power at the same voltage and can be 110 volts AC or 220 volts AC for larger vessels.
When you install a isolation transformer you are making a new power source for the boat. ABYC states the Green ground wire and neutral white wire will be connected together at the power source and only at the power source. As far as the shore power side of the isolation transformer is concerned. The green ground wire is terminated at the transformer at the head of the dock and does not cross over to the boat side once a isolation transformer has been installed. Therefore by installing an isolation transformer you uncouple the vessel from all the other boats that share the same power source.
An Isolation transformer works in both directions. If your boat has stray current issues and trips the ELCI breaker on the pedestal. An isolation transformer will keep the stray current limited to your vessel and keep stray current from exiting your boat via the ground wire.