About 20% of the plastic in the ocean is estimated to have come from boats, while the other 80% has come from on land, where it’s washed down by rivers or blown out by the wind.

The largest pieces of plastic—especially fishing lines and nets—are dangerous to boats because propellers can get tangled in them, and to wildlife because they can get stuck in them.

• Use fewer disposable items
  The single most important thing you can do is to use less plastic in the first place, so less is made and less is thrown away. Think about all of the throwaway items that you encounter in a day. Do you really need a new plastic water bottle every time or could you just get one long-lasting one and keep using? Could you take a reusable mug to the coffee shop, or reusable plates to that picnic? Why not bring a reusable bag the next time you go shopping? If you’re not used to doing these things they may seem like a lot of hassle at first, but it won’t take long for them to become second nature.
• Re-use things, even if they were meant to be disposable
  Remember that you can re-use even a lot of things that were meant to be used once. Try refilling a plastic bottle, or washing up a plastic plate and using it again. Or if you want to be more ambitious, try upcycling: making something better from stuff you would otherwise have thrown away.
• Use alternatives to plastic products
  Many things are made out of plastic when they don’t have to be. This can be bad for you, because of the toxic chemicals contained in several kinds of plastic, and adds to the garbage problem because the plastic itself lasts so much longer than the useful life of most things made out of it. If you use wood or paper instead of plastic—such as in more old-fashioned or hand-made children's toys—then the material will break down relatively quickly if it ends up in the sea, instead of lasting forever. If you use metal or glass—for reusable containers, for example—it still lasts a long time, but because it isn’t blown around or washed away as easily it’s much less likely to end up in the ocean. More natural materials also do less harm wherever they end up, because they are more like what plants and animals are adapted to.
Make sure that the plastic you do use gets recycled
Recycling is not a perfect solution. It uses a lot of energy, not all plastics can be recycled, and not all plastic products can be made with recycled material. At the same time, every piece of plastic that does get recycled has been successfully kept out of the ocean, and lets one less new piece of plastic be made. So whenever you do find yourself throwing away a piece of plastic, see if it can be recycled. If it can’t be, then at least make sure it does get collected properly, rather than just throwing it outside. Note that exactly what can be recycled and how it should be collected is different from place to place - you’ll have to find the right information for where you are.
Ask companies to waste less
A lot of the plastic we use is packaging, and a lot of it is completely unnecessary. You can’t single-handedly stop it from being used, but companies do listen to their customers, so if something you use comes with a lot of wasteful packaging try writing to the supplier. Once you’ve done that yourself, see how many other people you can convince to do the same. It usually takes more than one person’s comments to make a difference, but you might be surprised by how easy it is once you get a group of people interested.
Help scientists measure the problem
Anyone with a smartphone can download the Marine Debris Tracker app, which lets you report garbage you see in the water so that scientists can better understand exactly how much is out there, where it comes from and where it ends up.
Join a cleanup
Join the International Coastal Cleanup, or if there’s no event near you you can start your own. You can probably also find local groups organizing regular cleanups of shorelines or rivers where you are, and if no-one’s doing it then you can start one.

• Many places have banned plastic bags, which removes one of the bigger sources of plastic pollution.
If you don’t think an outright plastic bag ban would work where you are, you could push for a fee on throwaway plastic bags. Even very small fees make people more likely to bring reusable bags with them.
If plastics aren’t recycled where you are, you can help change that. Here are some suggestions for how to go about it.
Tell companies you buy things from to make them modular and repairable, so that you don’t have to throw something away as soon as one part stops working.
Promote Cradle-To-Cradle design and manufacturing. This means that manufacturers take responsibility for what their products will become even at the end of their lives. Very few things really need to become waste, if they are designed right in the first place.
If you want to see a really comprehensive set of policies that would work together to almost completely solve this problem, take a look at this action plan from California.

• Plastic Pollution Coalition - a global alliance of individuals, organizations and businesses working together to stop plastic pollution and its toxic impacts on humans, animals and the environment.
The United Nations Environment Programme is developing a “global initiative on marine litter”
Algalita Marine Research Foundation researches the extent of the problem, educates the public and promotes watershed restoration.
The Monterey Bay Aquarium spreads awareness of the health of our oceans and all kinds of threats to it.
The Ocean Conservancy has a comprehensive Trash Free Seas program