Vice sails to the North Pacific Gyre, collecting point for all of the ocean's flotsam and home of the Great Pacific Garbage Patch: a mythical, Texas-sized island made entirely of our trash.
As long as it's existed, the middle of the Gyre has been a naturally occurring point of accumulation for all the drifting trash in its half of the ocean. Once upon a time, flotsam circled into the middle of the Gyre and (because up until the past century everything in the world was biodegradable) was broken down into a nutrient-rich stew perfect for fish and smaller invertebrates to chow on.
The problem with plastic is, unless you hammer it with enough pressure to make a diamond, it never fully disintegrates. Over time plastic will photodegrade all the way down to the individual polymers, but those little guys are still in it for the long haul. This means that except for the slim handful of plastics designed specifically to biodegrade, every synthetic molecule ever made still exists.