Answer:
Water freight is a very important method of transportation and is the second cheapest (railroad is the cheapest). Huge volumes can be shipped at relatively low prices which is extremely important for raw materials and commodities.
The problem with water freight is that it is relatively slow though. Another problem that water freight faces is that it is cheap for medium and long distances, but uneconomical for short ones.
A great impediment for the technological progress of water freight is that most ports are obsolete and have not been updated in many years. Updating them is very expensive and many of them are public ports which doesn't help either.
Most new carrier ships (which are very high tech) are probably too big to fit into most US ports, so even if a carrier company invests huge amounts of money in them, where will they them? Technological progress must start with the ports, then water carriers should improve.
Another problem is that regulation is very loose in the US, especially regarding maritime ports.
