It's still not a lot of energy though. Some rough napkin math for how far this would get you is below:

Typical medium size cargo ships in the Panama Canal travel around 25 knots burning 63000 gallons per day of fuel with 5000TEU of cargo. That's roughly 600mi/63000gal or 1142miles per ton gallon. That Silverado EV somehow weighs 4 tons (totally safe to be driving at highway speeds), so this is the equivalent of roughly 285.5mpg per Silverado. The Silverado is 67mpge on its own, so the ship is just over 4x as efficient (and slower which is ignored here but would impact the vehicle efficiency).

So using the Silverado's 450 mile optimal range we can say it has at most an optimistic 7 gallons equivalent fuel in its 200kWh battery. 50 MWH would be enough for a theoretical 1750 gallons equivalent if efficiency were the same. But for the efficiency difference this corresponds to a 4.2x improvement to 7350 gallons equivalent. Therefore this is enough to run that typical ship above for 2.8 hours. So with 65000 tons of cargo in the above ship to do a 200 mile route this ship would need roughly 3x as large a battery. More likely it will just carry ~1/3 the cargo or have charging stops en-route.

The 19.4km/h top speed of this ship suggests they're well aware of the extremely limited range this will have for its size and it sounds like the Shanghai to Nanjing route will be pushing it's limits despite being less than 200 miles.