"The rule is, don't pick up anything smaller than your fist," Gilmartin told a team of volunteers. "Otherwise, it'll take forever. We'll never be done."
Noni Sanford reached down, scooped up a handful of beach sand and let it trickle through her fingers. Most of the grainy mix was bits and pieces of plastic. The beach itself, it seemed, was turning into plastic.
Cleanup efforts in Hawaii and elsewhere have focused on "ghost nets," tangles of abandoned fishing lines, nets and traps that snare and kill marine life.
The National Oceanic and Atmospheric Administration dispatches scuba divers every year to cut tons of these deathtraps off Hawaiian coral reefs. It's dangerous and costly work. In July 2005, a 145-foot charter vessel brought in to haul away nets ran aground on the reef at Pearl and Hermes Atoll, about 100 miles from Midway. The ship was lost. The Coast Guard flew the 23 divers and crew 1,200 miles back to Honolulu.
If it were easier to find them, it would make sense to round up the medusas of nets and synthetic lines at sea before they snagged on coral reefs and endangered monk seals and other coastal wildlife.
But the Pacific spans millions of square miles, and even the debris circulating in the Eastern and Western garbage patches is often diffuse and hard to see, bobbing just below the surface.
Connecting the two patches is a ribbon of oceanic highway that stretches 6,000 miles, an extension of Japan's Kuroshio Current heading east. Oceanographers call this the Subtropical Convergence Zone, where the cold, green, heavier waters from the north slide under the warm, blue waters of the south.
A team of scientists working on NOAA's GhostNet Detection Project suspected that flotsam collected along this line, making it an ideal place to concentrate cleanups. Yet they couldn't be sure. They needed to see it.
The team got its chance last year, after persuading NOAA to lend them an instrument-packed, four-engine reconnaissance plane often deployed to study hurricanes. Wearing life jackets while flying 1,000 feet above the ocean's surface, observers were positioned at windows to spot nets and floats. They were to call out each sighting over the plane's intercom. Others were poised to jot down the location of each sighting.
"When we got into it, we couldn't write fast enough," said Tim Veenstra, an Alaskan pilot and private researcher working with government scientists. The meandering line of buoys, nets, life rings, buckets and other castoffs stretched for hundreds and hundreds of miles — until the airplane had to turn back.
"It was sort of a bittersweet feeling," Veenstra said. "Sweet in the fact that what we had postulated was proven true. Bitter in the fact that there was actually that much debris floating around."
Tuna fishermen have long known about the convergence zone and the debris. They know that fish like to congregate beneath anything that floats.
Off the southern tip of the Big Island of Hawaii, recreational fishermen like Guy Enriques will race miles offshore to fish beneath the flotsam.
It's important to get close to the trash, but not too close, Enriques explained, or the nets and lines will wrap around a boat's propeller.
He said the best fishing was around what looked like an enormous metal garage door floating just below the water's surface. Even some charter boat skippers learned of that one, Enriques recalled, and took fishermen there day after day, until it vanished.
But it wasn't a garage door. He and other fishermen were looking at the top of an 8-by-40-foot cargo container that fell off a ship. Such containers can float for as long as nine months. Until they sink, they are the bane of sailors in fiberglass boats who watch for them like icebergs on the high seas.
Charles Moore, a member of the Hancock Oil family, was on his way home from the Los Angeles-to-Hawaii Transpacific Yacht Race in 1997 when he took a shortcut through the Eastern Garbage Patch. It's a place that sailors usually avoid because it lacks wind.