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The cleanup system is supposed to work like this: After the boom detaches from the towing vessel, the current is expected to pull it into the shape of a “U.” As it drifts along, propelled by the wind and waves, it should trap plastic “like Pac-Man,” the foundation said on its website. The captured plastic would then be transported back to land, sorted and recycled.

The boom has an impenetrable skirt that hangs nearly 10 feet below to catch smaller pieces of plastic. The nonprofit said marine life would be able to pass underneath.

But the ocean can be unpredictable, and simulation models are no guarantee of future performance.

“There’s worry that you can’t remove the plastic without removing marine life at the same time,” said George Leonard, chief scientist at the Ocean Conservancy. “We know from the fishing industry if you put any sort of structure in the open ocean, it acts as a fish-aggregating device.”

Small fish, drawn to a new structure, can attract bigger fish, he added, creating an “entire ecological community.”

It is unclear how well the boom would fare on the open ocean, where it faces high winds, corrosive salt water and other environmental challenges. And then there’s the question of whether it is possible to clean half of the garbage patch in just five years.