"We know very little about how the winds and the current push drifting objects like derelict boats and human bodies around the seas," says Curtis Ebbesmeyer, an oceanographer in Seattle who has been leading efforts to track the ducks' progress. "It's an oceanographic blind spot - oceanographers aren't too good at measuring right at the sea surface." And this is where the toys come in. Ebbesmeyer and his colleague, James Ingraham, a scientist at the National Marine Fisheries Service, have been carefully recording each reported sighting of the plastic toys.

The first find was in November 1992, when six were washed up in Alaska, some 3200 kilometres from where they were originally cast adrift. By alerting beachcombers and lighthouse keepers, and publicising their quest in local newspapers, the duo managed to track down hundreds more beached toys over an 850-kilometre stretch of shore during the next year or so. They then plugged the results into a computer model that Ingraham had devised to simulate the movement of the sea surface as it is buffeted by the winds. The model (called Ocean Surface Currents Simulation, or Oscur) uses measurements of air pressure going back to 1967 to calculate wind speed and direction, and the surface currents produced. "We model the changes in ocean circulation year by year and then apply that to fisheries problems," Ingraham says. The surface currents drive the top 50 metres or so of seawater around, and this is important for fisheries management as it contains the drifting eggs and larvae of spawning fish. "It's kind of a sideline for me to do the debris drift, but it's been more fun," he admits. The reports of the washed-up toys were useful in two ways. First, they allowed the scientists to check the performance of their model and to improve it. By pinpointing the exact place where the toys entered the sea from the ship's log, Ebbesmeyer and Ingraham could see how closely the computer predictions of where and when they would strike land matched the actual finds on the Alaskan coast.

Second, the researchers could run the computer simulation forward for a few years and see where the miniature fleet would head next. The last toy sighting was in Alaska in late June, but the model predicts that, by now, some will probably have floated off south towards eastern Asia and Hawaii. Others would have drifted north, passing into the Bering Sea. From there the currents should have carried them through the Bering Strait, spilling them into the Arctic Ocean sometime in the mid-1990s.

There the computer predictions end, but the researchers estimate that having entered the frozen Arctic Ocean, it would have taken the toys about five years to hitch a ride through the ice. "They would have grafted on to the ice, and the ice moves about a mile a day," Ebbesmeyer says. At that rate, the colourful flotilla should have emerged into the northern reaches of the Atlantic sometime in 2001, destined for the eastern seaboard of America, or for beaches from Iceland and Greenland down to Britain and Spain. "They should have been there for the last year or so, so in fact they're overdue," he says. "They're not going to come ashore as a big armada but they should be around." Ebbesmeyer estimates that a few hundred of the toys will have made it through the ice into the Atlantic, but so far there have been no confirmed sightings on either side of the pond.

"I've been getting reports from the Atlantic," he says. "People send me ducks from the north Atlantic in the mail but they've never been the right species." The ducks he's waiting for are stamped with "the first years" and will have faded to white. (The red beavers are also a pale shadow of their former selves, though the turtles should still be blue and the frogs green.) The idea of these five-centimetre high pieces of plastic successfully negotiating the Arctic Circle may seem farfetched, but global warming means that it's definitely possible, says Roger Proctor, of the Proudman Oceanographic Laboratory in Birkenhead, England.

"This is a new phenomenon as a result of the melting of the ice," he says. "Things from the Pacific are appearing in the Labrador Sea, coming round the top of Canada through the northwest passage." And from there, it's only a few months' hard drift to the open waters of the Atlantic Ocean. Proctor, who also works with computer simulations of ocean circulation and currents, cautions that it will be difficult to extract any useful scientific data from ducks that people may find washed up on the British coast. The pieces of plastic have been at sea for too long and nobody really knows what has happened to them since passing Alaska. "A lot of these toys might have been stuck on a beach somewhere for months before being washed off by a big storm," he says. "It's rather difficult to build that into a model." Oceanographers generally use more hi-tech toys to monitor ocean currents, such as buoys fitted with satellite tracking devices. But these are expensive - up to £1000 ($A2490) each - and that means only a few hundred can be deployed in one place at a time. "It's more accurate to use satellite buoys," Ebbesmeyer agrees. "But I think you can also get useful results from very large numbers of inaccurate drifters."

And of those, there is no shortage. As well as tracking the ducks and their friends, Ebbesmeyer and Ingraham followed the journeys of 100,000 toy cars and balloons, 34,000 ice hockey gloves and five million pieces of Lego, spilled from ships over the years. Most recently, they have been collecting information about 33,000 Nike shoes that slipped from a ship off the California coast in December last year. And this is not the first time. In 1990, the same footwear company lost 80,000 shoes further out in the Pacific. Within two years, everything from children's trainers to hiking boots were washing up as far away as Hawaii. The shoes were still wearable, even after all that time in the water, but only if the other one of the pair could be found, as partners were not laced together. (In case you were wondering, it's not that Nike are particularly careless with their wares - they are simply one of the only companies that will talk to Ebbesmeyer when they lose a shipment overboard.) In that case the researchers plotted the landing spot of about 1600 shoes - about 2 per cent of the shoes that entered the water - as good a rate of recovery as any oceanographer has when deliberately releasing objects to measure ocean drift.

It all sounds jolly fun, but Ebbesmeyer stresses there is a serious side to the work - highlighting the risk posed by the thousands of containers that fall off ships. "There are 50 of these big steel cargo containers floating in the Atlantic at any one time and they're definitely a hazard," he says. "The container companies don't tell me because they don't like to talk about accidents." He estimates that between 2000 and 10,000 containers are lost overboard every year, many of which spill open and release their contents into the sea. These accidental experiments over the years have helped the Seattle pair to improve their computer model so much that they can now predict the drift of an object for decades into the future. "We're now finding out that drifting objects can stay at sea for as long as 30 years without ever touching land," Ebbesmeyer says. Objects spilt in the right spot will get sucked into a huge, never-ending elliptical orbit between North America and Japan. "Quite a few go round and round and just never come ashore, and this is a result that is totally unexpected," he adds. Modelling the drifting cargo is not as simple as it sounds. Different objects float higher or lower in the water and so travel at different speeds because they are blown more or less by the wind. To account for this, each object in the model is given a wind factor: the ducks are reckoned to travel about twice as fast as the water, while a submerged Nike shoe goes about 20 per cent faster. In this way, the computer simulation used on the ducks can predict the drift of other objects that may fall into the sea, such as a human body.

Ebbesmeyer has worked with the police on tracking floating human remains in several investigations, one of which remains open. In 1982, a human skeleton was washed up in Hawaii still wearing its marine survival suit, but missing its left arm from below the elbow. By running the computer model backwards from that point, Ebbesmeyer has calculated that the body entered the water three years earlier off Alaska near the Arctic Sea. "Still to this day I'm trying to find out who he was," he says. The computer also predicted the final resting place of George Karn, a crewman lost from a fishing boat accident in the Bering Sea in 2002. Last month, Karn's jawbone and survival suit were found washed up on a remote island off Alaska. "We just figured out where the boat caught fire and then let the model run forward," Ebbesmeyer says. "It went right to the island where the remains were found."

He also tracks less gruesome discoveries, such as an empty, barnacle-covered boat that washed up last month on the coast of south-west England. It turns out that the boat, called the Dauntless, had been adrift for an astonishing 927 days since being lost from a luxury yacht during a storm in the Bermuda Triangle in November 2000. But at the moment what Ebbesmeyer really wants news of is a little yellow duck - or frog, beaver or turtle. "The person who finds the first one is going to make a big splash," he says. No reward is offered but the finder could become something of a celebrity, at least in beachcombing circles. - Guardian