This activity introduces students to the processes that break marine debris plastic down into small sizes: photodegradation and mechanical degradation. Students assess where particulates are suspended in the water column (premade plastic slurry). Next, the slurry is mixed into a tub of water that is designed to mimic seawater and students take samples to assess the amount, size, and type of the particulates. Students relate this activity to what they might actually find in the ocean. They will assess the difficulties of sampling and the limitations of the activity. Students are evaluated by their explanations of the abundance of plastic in the oceans and assessment of potential impact of plastic micro-debris to the health of marine ecosystems.