Imagine living a thousand meters below sea level surrounded by darkness but for a few bioluminescent rays of light. Now imagine living in a clear mountainous lake three thousand meters above sea level where the plethora of light can cause blindness anytime. There are many examples of animals that have adapted their vision to cope with different light conditions, yet little is known about the molecular basis of these adaptations. Thanks to the advent of New Generation Sequencing Techniques, it has now become feasible to study the evolution and function of vision, along with its underlying molecular machinery (opsins and their regulatory elements), one-on-one, in nature. Here, we report transcriptome based functional analyses of opsin expression in more than 30 fish species. These species were chosen based on a comparative dataset looking at visual evolution in 100 fish genomes spanning the teleost phylogeny. We show that the expression of opsins is very dynamic including co-expression patterns and retinal regionalization (using in-situ hybridization), which correlate with the light environment and/or visual tasks of different fishes. In particular, several species have evolved ingenious strategies to adapt to extremes of their photic environments. These include three independent cases of multiple rhodopsin use in species that colonize light deprived habitats, which may well be the first evidence for ‘true’ rhodopsin-based colour vision in vertebrates. Understanding how fish perceive their world and how this allows them to adapt to different environments is crucial for future management purposes, especially since many fish species are facing imminent danger due to anthropogenic activities.