When the Department of Transportation was created in 1966, Congress entrusted it with offices and agencies representing every way of transporting people and things save one. Now, 15 years later, it appears that the merchant marine will join the other movers.

A bill is working its way through Congress that would transfer the Maritime Administration (usually known as MarAd), its $600 million in shipbuilding and ship-operating subsidies and its 1,350 employes from the Commerce Department to DOT.

The proposed shift comes at a time when the problems of the merchant marine, long deferred, demand attention. They relate not only to the ability of one of the world's great trading nations to move goods, but also to providing reliable shipping support for the Defense Department in an emergency and the skill of U.S. industry in competing with foreign operations that are government-owned or subsidized.

The idea is being greeted as wonderful, even by many of the groups who battled successfully in 1966 to keep MarAd out of DOT despite the best efforts of President Johnson and his point man on the issue, Joseph A. Califano Jr.

Why the change in attitude?

Frank Drozak, president of the Maritime Trades Department of the AFL-CIO, expressed most succinctly an opinion heard from labor and management, builders and operators. "I think we'll get better recognition" at DOT, he said. "We've never had anybody at Commerce who cared whether we lived or died."

There is another factor: Transportation Secretary Drew Lewis's apparent understanding of maritime problems and support for that industry. Albert May, executive vice president of the Council of American Flag Ship Operators, said that Lewis "has been very dynamic, taken a great deal of interest in the industry, and Commerce has taken no interest whatsoever." That could be because Lewis and Commerce Secretary Malcolm Baldrige agreed early in the Reagan administration to support the change.

From an organizational point of view, a shift to DOT would appear to place the issues in the most logical place because maritime problems are closely entertwined with national policy on other forms of transportation.

For example, one of the major issues in making the United States the Great Exporter of coal is the need to improve port and railroad facilities dramatically. The Coast Guard and the Federal Railroad Administration are already in DOT and both of them have major roles in dealing with those problems.

Despite the logic, maritime interests have long regarded a move of MarAd to DOT as a threat. The fear was that MarAd would be swallowed whole as DOT pursued more glamorous and popular programs, particularly those run by the Federal Aviation Administration and the Federal Highway Administration.

Lewis has done some stroking to calm that fear. MarAd, he said, "will have an equal ranking with every other mode" of transportation. If the shift is approved, "there will be a voice in the administration for maritime policy," he said.

The most important issue is probably the question of what to do about MarAd's subsidy program. As a matter of theology, Republican administrations do not like subsidy programs, and the programs in MarAd require big dollars.

The construction and reconstruction subsidies -- the differences in the cost of having a ship constructed or rebuilt in a U.S. shipyard -- totaled $265 million in 1980; the operating differential subsidy, which seeks to equalize the disparity in operating costs between American ships and their foreign competitors caused primarily by higher labor costs, totaled $341 million in 1980. In addition, the federal government has $7.8 billion outstanding in loan guarantees to finance shipbuilding.

The operating subsidy is part of a 20-year program that is essentially untouched in the current congressional budget wars. The construction subsidy, however, has been cut dramatically in various proposals on Capitol Hill and may still have to be worked out in a House-Senate conference.

Should those subsidies be continued, modified or terminated? This is a question Lewis and his advisers will have to face and Lewis was not specific when asked how he intends to address it. He suggested that some assistance to the merchant marine might be appropriate for the Defense Department because of its reliance on the merchant fleet in an emergency.

Defense is known to be worried about the problem. Secretary of the Navy John Lehman, in a commencement address at the Merchant Marine Academy (part of MarAd), called the current condition of the merchant marine a critical national problem.

"After World War II, American ships carried 60 percent of this country's trade," he said. "Today that figure is less than 5 percent. . . . In my considered judgment, we cannot ever hope to have true maritime superiority as long as we are subject to the political reality of significant dependency on foreign nations for our world trade. This must be changed."