Answer:  They have all been spilled in the ocean in maritime accidents during the past few years and have turned up on beaches thousands of miles from where they were lost. 

And that's not all that the tides bring in:  computer monitors, toilet seats, bales of marijuana, surfboards, lightbulbs, and toxic-waste containers are among the other items that a committed beachcomber might find.  Curtis Ebbesmeyer is such a beachcomber.  He is also a researcher who studies long-distance floatables in order to understand ocean currents.  Ebbesmeyer, who lives on the Oregon coast, had been studying ocean currents for a number of years when, in May 1991, he learned that hundreds of brand-new (though somewhat soggy) Nike sneakers were washing up on beaches in his area.  In fact, they were arriving in such quantities that beachcombers had begun to hold swap meets to match left and right shoes of the same size.

Unlike most of the beachcombers, who were mainly interested in finding shoes they could wear or sell, Ebbesmeyer figured that if he could find out where the sneakers originated and where they turned up, he could use them as data for studying ocean currents.  In fact, he soon learned that the sneakers had been on a container ship en route from Korea when the ship encountered a major storm on May 27, 1990.  Twenty-one containers were washed overboard, including five that contained 80,000 Nikes.  The sneakers were even marked with serial numbers for convenient identification!  With the help of volunteer beachcombers in many countries, Ebbesmeyer and his colleagues managed to recover about 2.6 percent of the floating sneakers, mainly in North America, on beaches from Northern California to the Queen Charlotte Islands in Canada.  A few have turned up in Hawaii, while others have been found on Wake Island, the Philippines and Japan.  Some apparently circumnavigated the North Pacific and wound up back on the coasts of Washington and Oregon in 1996 and 1997.

Tracking the paths of these sneakers and other floating junk (much of it plastic) that washes up on beaches around the world has helped to develop and refine models of ocean circulation and provided an inexpensive and valuable adjunct to the drift experiments that oceanographers conduct with modern, high-tech (and much more expensive) tracking devices.

Links:
= highly recommended

Online edition of Curtis Ebbesmeyer's newsletter, Beachcomber's Alert.  See the archive for more information on the Nikes and other objects his associates have tracked.  The site also has information on how the objects help track ocean currents, and on what to look for on beaches and how to report what you find to his group.

Kevin Karjick, "Message in a Bottle." Illustrated summary of an article about Ebbesmeyer's work in the July 2001 issue of Smithsonian Magazine. 

"Rubber Ducks Go Swimming," a two-minute radio clip from the American Institute of Physics explaining how floating junk helps scientists study ocean currents. (In RealAudio)

"Teich's Tech Tidbit for June 4, 2001 -- Containerized Shipping:  Thinking Inside the Box" describes more conventional uses for container ships.  (As I wrote that Tidbit I began to wonder what might happen if a container ship hit really rough seas.  This week's Tidbit provides the answer.)

"For Beachcombers, Alaska is paradise:  From 'Rugrats' to Coconuts, Seaborne Treasure Floats In," by Kristan Hutchison of the Juneau Empire, in The Seattle Post-Intelligencer  (April 13, 2000).

Sea beans and drift seeds are hard, buoyant fruits and seeds that fall from trees into rivers (mainly in the tropics), are carried downstream to the ocean, and drift long distances.  Sea bean enthusiasts pick them up on beaches far from their origins, study them, use them to make jewelry and art objects, or just collect them.  Author Cathie Katz has a large and interesting site devoted to the subject (seabean.com) and the Brevard Museum of History and Natural Science in Cocoa, Florida, also has a site with interesting and useful information.  And here are some very nice photos of a drift seed collection from the Florida Keys.

Law offices of Countryman and McDaniel, "Overlooking Runway 25 - Right, at Los Angeles International Airport." This firm specializes in ocean and air logistics; its huge, but somewhat awkwardly-designed, site has lots of information and photos of maritime cargo disasters.  See, especially, the "Gallery of Cargo Loss."

Some photos of the APL China, a container ship, after its encounter with a storm in the North Pacific in November 1998.  (Source of photo at the top of this page.)

Glass fishing floats have long been a beachcomber's collectible.  This is a site that one collector has set up to showcase his collection.  Included are photos, books, and information on collecting glass floats.

Sites for:
              Nike sneakers (and other products) -- non-waterlogged variety
              Rubber ducks for your hot tub or spa (baseball players, glow in the dark ducks, etc.)
              Lego toys