Long-term data are key to understanding how species, communities, and habitats change over time. Citizen science programs can support data collection at greater spatial and temporal scales than other types of scientifically collected data which tend to be project-specific and are often tied to short funding periods. This is particularly true for environments that are difficult to sample such as subtidal ecosystems. Reef Environmental Education Foundation (REEF) citizen science SCUBA surveyors have been collecting fish, invertebrate, and algae data in British Columbia since 1998. This study demonstrates how citizen science data from REEF can be used to answer scientific questions via case studies, the first on Lingcod (Ophiodon elongatus) population responses to management decisions and the second on detecting rockfish species (Sebastes spp.) young-of-year abundance pulses. The results of these case studies suggest that data from REEF, despite limitations, can be used to improve our understanding of nearshore marine ecosystems.