1. You can try to use less single-use disposable plastic. Whether it’s bringing a cup to your local coffee place to declining a straw, or keeping reusable grocery bags in your car and using a refillable water bottle at the gym, keeping things out of the waste stream is the best way to stop plastic pollution.
2. You can be a selective consumer. Choose products that come with less plastic packaging, even if they're a little bit more expensive or a little less convenient.
3. You can also Take part in a beach cleanup in your area.
4. One other thing you can do is find a search engine that you like and that cleans up the ocean. One I have heard of is called Ocean Hero!