The bold is what kids can do:
Research on the topic. Researching and spreading awareness on the topic, the problem could go down.
Use cars less. I know that we all have places to go, but every once in a while it doesn't hurt to walk or bike to help lower fossil fuels use and oils ending up in the ocean.
Clean up your local beaches and oceans
Talk to officials
Join organizations such as Ocean Conservancy, Oceana, Surfrider Foundation and more
Use reusable plastics. Millions of tons of plastics are dumped into oceans each year, due to improper recycling and other reasons.
Tote bags instead of plastic grocery bags
Reduce, reuse, recycle and never forget that rule