What Happens to Plastic in the Ocean?

If you were in a boat whilst in the middle of one of these waste patches - you will not even realise it. People imagine the trash bobbing up and down in a huge carpet like structure/formation? No, think again. The trash is all broken down to it’s most ecologically harmful form (outside of burning, maybe) - micro plastics. 
The plastics are caught in a current system that is twice the size of Germany by area. There isn’t much you can see with the naked eye and analysing a sample at the area with the highest density will find only 4 particles of plastic per 1 cubic meter of seawater - and that is considered highly densely packed in pollution terms (and an ecological disaster). 

So you in your boat smack in the middle of the densest oceanic plastic patch in the pacific would not find any plastic even if you scooped up cup of sea water. The oceans are that large. But this issue even at this point is terrifying.