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  At some point we all have to memorize the names of the earth's oceans . But in reality all these waters are connected, so how do we know where one body begins and another ends. Just follow the trash, because the location of   sea-ferrying garbage can be used to define the ocean's borders. That's according to a study in journal chaos¹. Historicall speaking the planet's waters were   partitioned into discrete² oceans for reasons that are geographical³, historical or even cultrual. To approach the problem from a more anatomic perspective, researchers came up with a model of how surface waters move, which is where the rubbish comes in. Flotillas and flots are formed by currents that gather the garbage in large floating patches, but the currents also create barriers that minimize the mixing between different ocean regions. By modeling these  currents, researchers have redefined the borders of the ocean basins based on how readily their waters mix. They find, for example,that a sliver⁴ of Indian Ocean is really part of the South Pacific. The work should help track the ocean debris⁵ or even the spread of spilled oil, and it could change the way we see our seas.