Clip 10 of 12 does a really good job of showing and explaining how all of the plastics, when they begin to break down, become a confetti of little small pieces that are mixed the food chain with other sea life, plankton, etc.
TOXIC* - GARBAGE ISLAND - Part*10*of*12 - VBS.TV
There's no "money shot" of a huge swath of immediately visible debris, but upon skimming the water for test samples, what they find is much much worse.
If you don't watch all parts,
10 of 12 gives a good summarization.