The correct answer to this open question is the following.
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A possible explanation for why some shoes drifted northward along the coast while others drifted southward is because the ocean currents are different and can easily make an object to change direction, depending on the currents. Heavy storms can also be a factor in the changing of the current and the objects.
That is what happens with the May 1990 incident with a cargo ship from Korea that was sailing to Alaska, United States. A heavy storm made 21 containers fall to the sea and 5 of them broke, releasing approximately 60,000 tennis shoes.
Although the incident was close to the shores of South Alaska, it took them almost nine months to get to the shores of Oregon, and Washington.
The oceanic currents affected the direction of the tennis shoes.
