Oh, it's a cable-guided ferry. Since it already has a guide cable, it may as well be cable powered, too. That's not uncommon, but usually the power is transmitted mechanically, like a ski lift.

Brighton Beach in England once had an electric-powered sea-going railroad with an 18 foot gauge. A ferry running on railroad tracks. More of an amusement ride than a means of transportation, like some Disney water rides that run on tracks.