Remember that government ad that went "Ang basurang itinapon mo, babalik din sa 'yo?" (The garbage you throw away will come back to you).
What do you think happens to all that plastic that nations---especially "first world countries" that consume vast amounts of these products---dump into the water? They float aimlessly and get tossed and turned into the ocean's currents and recurring tidal patterns. One well-known is the geophysical pattern called the North Pacific Gyre.
Believe it or not, that's exactly what's been happening to a VERY large mound of garbage that's been accumulating to the size of the US state of Texas. Practically a floating island of non-degrading plastics and other kinds of trash really. It's a not too subtle reminder of the harmful impact we've been doing with our environment.
As plastic doesn't degrade but does break down into smaller and smaller bits over time, how can all that floating micro-bits of plastic impact the ecosystem? Well what do you think the fish will eat? I imagine eating toxic fish isn't very healthy.
Read here for more info.
What's this humongous pile going to cost humanity later on?