Since their introduction in the 1950s plastic products have been widely used. Plastic particles disposed on land eventually make their way to coastal lagoons and beaches. Organisms often mistake plastic and smaller pieces known as microplastics for food and once ingested, they can cause multiple health problems. For this study, we determined the concentration and types of microplastics found in the sediment of two coastal lagoons in San Diego California. Sediment samples were collected from two coastal lagoons and beaches and sieved to remove shells, debris, and larger microplastics. A dense solution of zinc chloride was then used to float the microplastics above the sediment. The supernatant or liquid above sediment was filtered and imaged using stereoscope fluorescence microscopy. Fluorescent particles in the images that were interpreted to be micro-plastics were counted and categorized. Preliminary results show that microplastic concentration in the lagoons ranged from 0 to 3000 microplastics per liter of sediment. Greater concentrations were found in the beach areas facing the open ocean and the lowest were found in the inner lagoon. This suggests that sediment can act as a microplastic sink. These results provide us a better understanding of microplastic distribution near coastal lagoons and highlight the need for improved management practices to reduce plastic pollution which will improve overall organism, ecosystem, and human health.