Lake Marcel-Stillwater is located at 47°41′44″N 121°54′55″W (47.695443, -121.915236). According to the United States Census Bureau, the CDP has a total area of 1.3 square miles (3.5 km²), of which, 1.3 square miles (3.3 km²) of it is land and 0.1 square miles (0.1 km²) of it (3.73%) is water.