There's an article in a recent issue of IEEE Spectrum about a plug-in hybrid ferry: https://spectrum.ieee.org/transportation/marine/happiness-is-a-hybridelectr

There's an article in a recent issue of IEEE Spectrum about a plug-in hybrid ferry: https://spectrum.ieee.org/transportation/marine/happiness-is-a-hybridelectric-ferry https://spectrum.ieee.org/transportation/marine/happiness-is... It can cruise purely electric, although with just 100 kWh of battery capacity, the net result is a 30% reduction in diesel consumption.