There are ducks at Howard Beach, and herons farther on at Jamaica Bay, and odd watery vistas all the way from Broad Channel to Far Rockaway. The train travels on a causeway past what looked like sleepy villages and wood-frame houses, and it's all ducks and geese until the train reaches the far side of the bay, where the dingier bungalows and the housing projects begin. Then, roughly at Frank Avenue station, the Atlantic Ocean pounds past jetties of black rocks, not far from the tracks, and at Mott Avenue is the sprawling two-story town of Far Rockaway, with its main street and its slaphappy architecture and its ruins. It looks like its sister cities in Ohio and Rhode Island, with just enough trees to hide its dullness, and though part of it is in a state of decay it looks small enough to save.

That was a pleasant afternoon, when I took the train to the Rockaways. Out-of-season Coney Island, on the other hand, was populated by drunks and transvestites and troglodytes, and the whole place looked as if it had been insured and burned. Though it is on the other side of Rockaway Inlet, it is a world away from Rockaway Park.

The subway stations usually reflect what is above ground: Spring Street is raffish, Forest Hills smacks of refinement, Livonia Avenue on the LL looks bombed. People aspire to Bay Ridge and some people say they wouldn't be caught dead in East Harlem - though others are. The Fort Hamilton station leads to the amazing Verrazano-Narrows Bridge and the IRT No. 1 to a ferry landing. By the time I reached 241st Street on the 2, I thought I had got to somewhere near Buffalo, but returning on the 5 and dropping slowly through the Bronx to Lexington Avenue and then to lower Manhattan and across on the 4 to Flatbush, I had a sense of unrelieved desolation.

Not long ago, The Daily News ran a series about the subway called ''The Doomsday Express.'' It was about all the catastrophes that are possible on the New York system - spectacular crashes and floods with heavy casualties.

It is easy to frighten people with catastrophes - much harder to convince them that decay and trivial-seeming deterioration can be inexorable. The New York subway system is wearing out, and certain sections are worn out; a large part of it looks hopeless.

There is a strong political commitment to the subway, particularly among down-market Democrats anxious to identify with blue-collar commuters who have no choice but to take the subway. But only money can save it. To this end there is a plan called the ''Five-Year Capital Program'' of $5.8 billion, which won approval from a New York State review panel late last year. The money is to be raised through M.T.A. bonds and will also include Federal, state and city grants. It will be the largest infusion of capital in the history of the city's bus and subway system, and will involve fixing and buying cars and buses, retiling and cleaning and lighting stations, restoring maps, windows and signs, repairing tracks and elevated structures - all the day-to-day things which, because they have been ignored, have given the subway and bus system a bad case of arteriosclerosis.

Vital infusions of money aside, there is still the matter of the subway passenger. Most people who live in New York act as if they own the city: It makes some people respectful and turns others into slobs - and that is how they treat the subway. ''I pity you,'' people said when I told them what I was doing. But I ended up admiring the handiwork of the system and hating the people who misused it, the way you hate kids who tear the branches off saplings.