Harbor seals (Phoca vitulina) are one of the most commonly observed seal species along the U.S. East Coast. They breed in the northeastern United States and Canada and migrate seasonally in response to changes in water temperature and prey availability. During the winter months, harbor seals travel south and are increasingly observed in the Chesapeake Bay and surrounding coastal environments, including areas near the Bay mouth, barrier islands, and adjacent shorelines. While winter sightings are becoming more frequent, the full extent of seal distribution, preferred habitat areas, and timing of movement within the Bay and nearby coastal waters remain poorly understood. The Harbor Seal Spotting project compiles observations from boaters, fishermen, shoreline observers, and others who spend time on or near the water during winter. By documenting where seals are and where they are not, this project helps researchers map winter distribution patterns, identify frequently used areas, and detect changes in seal presence over time. These data can inform future research, conservation planning, and management efforts across the Chesapeake Bay region. Whenever possible, volunteers are encouraged to submit photos with their observations. Images help confirm species identification and may contribute to photo-identification studies that track individual seals based on unique markings.