In the classic 1967 film “The Graduate” a house guest tells a drifting Dustin Hoffman he has one word to say to him: “Plastics.” The guest says they have a great future.

They did. And they do. But the downside to plastics is that they stick around a very long time. And given too many humans’ propensity to simply discard plastic bottles and the like instead of recycling, plastic has become a serious environmental problem, especially at sea.

Ocean currents have herded immense campuses of floating plastics into massive artificial islands where the debris is slow to degrade and ensnares wild turtles, whales, dolphins, seals and other sea life. A 23-year-old Dutch college student named Boyan Slat was appalled by the floating plastic messes he encountered diving in Greece.

Now, after years of designing, fundraising and construction, Slat’s Ocean Cleanup Project is almost finished in Oakland, Calif. Next month he’ll set sail — well, actually, it’ll be dragged — out in the Pacific to one of the large plastic masses.

There, the idea is 2,000-feet of four-foot-diameter closed, floating tubes will drift passively and slowly in a U-shape through the plastic mess. The tubes suspend nine-feet of net skirting below intended to allow sea life to pass through but to herd large volumes of floating debris to the middle for removal and recycling on land.

USAToday has photos of Slat’s expensive brainchild, which gained foundation funding.

The project, which is illuminated by solar warning lights, is untried and like any new idea, has also netted a variety of skeptics eager to detail potential problems. The device could break apart in storms. It will not collect sunken debris.

Also, there’s a large contingent of environmentalists that says the focus should be preventing new debris. Think, for instance, municipal bans on plastic straws.

Richard Thompson is head of the International Marine Litter Research Unit at Britain’s University of Plymouth. He said:

If we consider cleanup to be a center stage solution, then we accept it is OK to contaminate the oceans and our children and our children’s children will continue to clean up the mess.

But there’s this: The loose campaign to stop the pollution of roadside litter really began in the 1950s with Americans’ postwar love affair with cars and travel on modern highways and Interstates. Now, there are hefty fines for littering and volunteer groups and municipal prison crews that clean roadsides.

But in those days, it was simply radio and TV appeals for manners, not to toss garbage from your car. Back then, my father paid me 25 cents an hour to pick up roadside debris near our rural home, using a nail in the end of a long stick. I can report that people threw away a lot of strange stuff.

It occurs to me now that if we’d postponed cleaning-up until Americans were trained not to litter, no vehicle could today make it through 55 years of accumulated debris on and along roads.

So, good luck to Boyan Slat. Imagine the bottle-deposit money he’ll reap.