Think start cleaning up the plastic and find a way to reuse them in a better way will need to start.
At most we need to teach people around us, and children especially that throwing any plastic to the river / sea is just not going to work well in the long run.
I am trying very hard to educate my siblings and finally one of them decided to bring along a metal container to pack food on her way to work, and pack food home.
My younger brother is still not listening. He just "conveniently" buy bottled water to consume, even though we got him water containers.
The only good part is that he started throwing the plastic into the recycle bin.
Malaysia (especially the state of Selangor and the Island of Penang) has declared no plastic bags used for grocery anymore.
It is so hard to get my senior citizen colleagues to pack food with present container because they tend to "not able to finish the food" and just pack up and throw. (food waste)
Bottom line this is human behaviour that must be changed.
Issuing taxes on countries with high polluting status is not helping when the citizens are not environment aware.