For 1500 passengers and 30 MWh (i expect they dont arrive 100% empty) this is 20kWh per person. If they travel 80 kilometers, thats 0.25 KWh/person/kilometer. Sounds OK to me (all values are guessed).
It is interesting to see how that compares to the much smaller Candela P-12 ferry shuttle. Candela is a an electric hydrofoil.
30 passengers, 336 kWh usable at max range, gives 11 kWh per person. Max range 72 km (40 nautical miles), 0.16 kWh/person/km.
Cats can be close to foiling. I suspect in this case the cargo has huge effect too.
I wonder what the charge time is? Will they be able to make 2-3 return trips per day or just 1?
There's an 'related stories' link down the bottom of the page with a bit more info. The ferry has a runtime of 90 minutes, and the regular trip takes "just over an hour", and a full recharge takes 60-90 minutes, with chargers at both terminals. So a return trip would take 2 hours + 2 charges, so somewhere around 4 hours. So I'd estimate it could do ~6 return trips per day.
Buenos Aires to Montevideo is ~200km so I guess they are going to Colonia del Sacramento, ~50km.