Ocean Plastics 

Macroplastics are plastics that measure over 5mm. They are usually visible. Things like plastic bags, bottles, cutlery, hardware, fishing line, polyester fabrics, Styrofoam, and food containers are the big ones. And all of these will eventually break down into microplastic. 

Microplastics are plastics that measures under 5mm. They can get extremely small because plastics are not biodegradable. That means when they break down they only get smaller, accumulating in the ecosystem. Above is from a tide pool in the greater Portland area.