This story comes from Science News via Boing Boing:
David Pescovitz: Fifteen years, ago a shipping container fell off a boat crossing the Pacific, spilling tens of thousands of rubber duckies, turtles, and other bath toys. The mishap was actually helpful for oceanographers who to this day occasionally find the toys and use their recovery location and time as data points in their study of ocean currents. This is just one example of how scientists count on floating junk in their efforts to map and understand subcurrents and other ocean phenomena. Interestingly, random bits of flotsam can sometimes work better than electronic devices designed for this purpose due to the limitations of battery power and algae growth that can block the sensors. From Science News:
Worldwide, about 10,000 cargo containers fall overboard each year. In most parts of the world, the dispersal of flotsam isn't of major interest to researchers. But along the bustling trade routes that link eastern Asia to North America, the tennis shoes, kids' sandals, hockey gloves, and other stuff that drops off ships is enabling scientists to fill in details of how the Pacific Subarctic Gyre works.
Often, the lost items float and can be readily identified as coming from a ship at a certain location. Recently, (retired oceanographer Curtis) Ebbesmeyer and his colleagues used almost a century of data from such floating objects to map the gyre's major subcurrents and swirls.
Now, for the first time, scientists have determined that a lap around the Pacific Subarctic Gyre takes about 3 years. That information, in turn, led Ebbesmeyer and his colleagues to identify long-term variations in water temperature and salinity in the North Pacific that hadn't been noted previously.
All this from studying flotsam...
...The flotsam-researchers' techniques may not seem scientifically rigorous, comments Richard Thomson of the institute (of Ocean Sciences) in Sidney. However, he adds, "with oceanographers, the more data, the better. ... [Studying flotsam] is one of the few ways to get it."
Link to the original story
And here's a link to a Wikipedia article on flotsam and jetsam, just in case you can't get enough of this stuff.