Go out in a boat on a June afternoon and you might notice something: how few commercial vessels you encounter in the span of a few hours. I’ll dispense with the exceptions right away-lobster boats and ferries are as plentiful as ever on Casco and Penobscot Bays-but otherwise, the amount of water-borne commerce is small compared to what it must have been in the past.

If you’re wondering why, the answer is obvious: technology and government policies over the past century and a half have encouraged Americans to use just about any means of transportation other than water. We built roads and bridges, we built railroads, we built Interstate highways; we built airports so if we’re in a hurry, we can fly. We gave the railroads land so they could lay their tracks, while we actually used tax dollars to build highways and airports. Moving stuff around in barges or ships is slow and risky; a lot of the time, it’s just easier to “ship” (we still use that old word, don’t we?) by truck, train or air.

This could all change, of course. As the price of fuel goes up, the cost of driving trucks over the roads rises; the cost of air travel rises faster; the disadvantages of loading cargoes on barges or ships begin to be outweighed by the cost savings.

Before you go out and invest in a floating cargo-carrier to make your fortune, however, please remember that cost and speed alone aren’t going to bring cargoes back to the sea.

Government policies will play as large a role as they always have: a decision to subsidize some other form of transportation (we’re spending federal stimulus money on a big I-295 paving project here in Maine right now) will affect shippers’ decisions in the future; likewise a future decision by the government to help maritime commerce in some way might bring us all back down to the sea. Just as the current recession has lowered the number of tankers (we’re using less oil) and the number of cargo and container ships (we’re importing fewer Toyotas) out there this year, a future boom in imports (world trade policy? value of the dollar?) could cause ocean shipping to blossom. There’s no way to know.

Still, there are some interesting instances of life out there on the sea lanes. Sail offshore between the Cape Cod Canal and Cape Ann, and you’ll encounter a bunch of large buoys and a big construction ship. This is the site of the offshore LNG facility being developed for the Boston region: tankers will come here, attach themselves to a floating buoy and pump their cargo into an undersea pipeline instead of steaming into Boston Harbor and unloading there. The arrangement’s sure to be more acceptable to the public than bringing a fully-loaded tanker carrying a potentially explosive substance into a metropolitan area. Using the offshore facility may mean fewer jobs for Boston harbor pilots and tugboat crews, but it should ease public fears.

Sail east on Long Island Sound past Bridgeport, Connecticut, and you’ll see a huge orange vessel, anchored not far off the north shore of Long Island. The 600-foot MV Barkland functions here as an extension of Bridgeport’s waterfront; coal ships from Indonesia deliver low-sulfur coal to the Barkland, which transfers it to barges that carry the coal to a power plant in Bridgeport. The reason for the arrangement: Bridgeport harbor is in need of dredging and is too shallow for big ships at the present time.  Wouldn’t dredging the harbor make things more efficient by eliminating the need for this transfer operation? Probably, but consider the externalities: likely public opposition to dredging, where to put the dredge spoils, concerns about big ships in a small harbor, competing uses for limited shorefront. We aren’t making any more waterfront suitable for deep-sea commerce; The Barkland is likely to stay where she is for a long time.

Big energy projects that affect the coast of Maine raise similar issues. There’s the case of Searsport and Sears Island, where the objections of well-connected summer people held off the development of a cargo port for decades, until the demise of northern Maine’s paper industry made the port uneconomic to build. Earlier, Sears Island had been the site of a proposed nuclear power plant and then a coal-fired plant, neither of which got built either. An LNG facility proposed in Casco Bay didn’t get very far; nor did an oil refinery put forth many years ago for Eastport. All of these projects were touted by developers as economic salvation; none got built when the real costs and externalities became apparent.

Is there a bottom line? If there is, it’s hard to discern. Using convenient forms of energy is likely to remain as popular as it is today; bringing in the fuel and using it to generate that energy is likely to remain unpopular and subject to pressure to do these things somewhere out of sight. Shipping fuel and other goods by water will make sense if it’s fast, efficient and safe enough, and if it’s really cheaper than other means of getting goods from one place to another. Right now it doesn’t make the sense it once did, but things will change again. They always do.

David D. Platt is former editor of Working Waterfront.