Tony Haymet, former director of the Scripps Institution of Oceanography, has heard hundreds of ocean cleanup plans. Late at night, over many beers, he's come up with a few dozen of his own. None of them, he says, has seemed likely to work. That includes this spring's offerings. A Dutch engineering student, Boyan Slat, envisions a contraption with massive booms that would sweep debris into a huge funnel. Songwriter and music producer Pharrell Williams wants to fund the monumental cost of any cleanup by turning recycled ocean plastic into yarn and then clothes.