actually, what the dude is describing (a large ship carrying containers over sea routes) already exists ... in fact, they're called container ships, and they sail back
and forth all over the world every day.
three things make the dude's idea impractical in this case:
1. using the Oriskany as a container ship is probably too expensive to turn a profit; and
2. container ships make money over the long haul; the longer the route (say, Miami to Liverpool) the better; a route from Jax to Miami is just too short; and
3. given the cheap alternative available (trucks on an overland route from Miami to Jacksonville), this wouldn't make any money.
also, land hauling along the same lines is very common. it's called intermodal transport, and railroads do it very well. they load the train with containers at point A and then take them to point B where they're hitched to trucks and off they go.
mike_s:
Truck ferries like this are very common in Europe to go between the UK and Ireleand, etc.
but note the absence of a competing land route. higher costs are accepted (and inevitable) because there is no other choice.