Sometimes the object spotted in the water is a snarled fishing line. Or a buoy. Or something that might once have been the lid to an ice box. Not once - not yet at least - has it been a clue.
Anticipation has repeatedly turned into frustration in the search for signs of flight MH370 as objects spotted from planes in a new search area west of Australia have turned out to be rubbish. It's a time-wasting distraction for air and sea crews searching for debris from the Malaysia Airlines flight that vanished on March 8.
It also points to wider problems in the world's oceans.
"The ocean is like a plastic soup, bulked up with the croutons of these larger items," said Los Angeles captain Charles Moore, who is credited with bringing attention to an ocean gyre between Hawaii and California known as the Great Pacific Garbage Patch, which is about the size of Texas.
The world's oceans have four more of these flotsam-collecting vortexes, Moore said, and the searchers, in an area 1,850 kilometres west of Perth, have stumbled onto the eastern edge of a gyre in the Indian Ocean.
"It's like a toilet bowl that swirls but doesn't flush," said Moore.
The rubbish patches are nothing like a typical waste dump. In fact, most of the rubbish can't even be seen: it's composed of tiny bits of plastic bobbing just below the surface.
The larger items also tend to be plastic and are often fishing-related, Moore said. Though, he added, he has come across light bulbs, a toilet seat, and, bobbing off the California coast, a refrigerator, complete with orange juice.
Seattle oceanographer Curtis Ebbesmeyer has been studying ocean debris for years. He said there are smaller collections of rubbish within the gyres. "If you go into a house you'll find dust bunnies," he said. "The ocean has a mass of dust bunnies, each moving about 10 miles a day."
Ebbesmeyer said he's fascinated by what happens to the waste that spews from the hundreds of shipping containers lost overboard from cargo ships each year. He said there's one that belches out Lego pieces onto the beaches of Cornwall in England. Another spilled 2,000 computer monitors. Another released thousands of pairs of Nike shoes.
Sometimes, he said, the containers themselves can become hazards as they float around for months, buoyed by plastic objects inside or the air trapped behind watertight doors. Waste also gets into the ocean after being washed down rivers or swept up in tsunamis, Ebbesmeyer said.
Scientists are particularly worried about small and seemingly ubiquitous pieces of plastic that can be from shopping bags, plastic water bottles, or other household items. Waves break the items up into smaller pieces.
Denise Hardesty, a research scientist for the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia, conservatively estimates there are between 5,000 and 7,000 small pieces of plastic per square kilometre in the waters around the country.
She said two-thirds of the seabirds she's performed necropsies upon have ingested at least some plastic, and one particular bird had swallowed 175 pieces.
"It takes 400 or 500 years for lots of plastics to completely break down," Hardesty said. "You even find plastics in plankton - that's how small it gets."
American sailor James Burwick said he's twice crossed the Indian Ocean from Africa to Australia. He said the sea was too wild to see much waste but he did feel bumps against the bottom of his boat, and an old fishing net once got caught around his vessel.
Wing Commander Andy Scott, of New Zealand's defence force, said the crew in a P-3 Orion scouring the ocean for flight MH370 on Saturday spotted about 70 objects in four hours.
Three were deemed worthy of further investigation but none turned out to be from the missing plane. One was probably a fishing line, another was the suspected ice box lid, and a third was some unidentified brown and orange material.
"A lot of the stuff we are seeing," Scott said, "is basically rubbish."