The visual pigments of fish are thought to be adapted to the variable spectral qualities of aquatic light environments. Most research on the role of natural selection on the evolution of rhodopsins and dim-light vision in fish has focused on variation among species and higher taxa. In this issue, Larmuseau et al. reveal substantial intraspecific sequence variation in RH1 (the rhodopsin gene) in sand gobies (Pomatoschistus minutus). Using population genetics and molecular evolution approaches, they detect positive selection on RH1 and find evidence for adaptation to local light conditions.