MARCUS ERIKSEN: “These are five sub-tropical gyres in the world where the majority of the plastic in the world accumulates.”

ANNA CUMMINS: “The gyre is formed by ocean currents that couple with the spinning of the Earth, the Earth’s rotation. And what happens is that you have, effectively, a massive whirlpool, this large spinning system, where debris can accumulate.”

Anna Cummins and her husband Marcus Eriksen set up a not-for-profit group called the 5 Gyres Institute. It helps researchers with studies of plastic pollution in the oceans. Cummins says plastic bags and bottles have little or no value after they are used. Most plastic waste can be found in solid-waste landfills or along rivers. A lot of this waste also washes out to sea.

CUMMINS: “This becomes a problem in the marine environment because plastics are designed to last forever. They don’t break down, they can’t be digested by marine organisms and they persist in the ocean for thousands of years.”

When sailing, Eriksen and Cummins gather objects from the ocean’s surface. Hundreds of things they caught have gone to a California laboratory for testing.

CUMMINS: “What shocked me the most on all these trips is to cross an ocean, to cross for thousands and thousands of miles, and find that every single sample we pull up has plastic.”

Some plastics stay in large pieces for a long time. But many break down into smaller particles.