This study represents the first nationwide assessment of marine recreational fishing in Spain. A new cost-effective approach was used to collect fisher’s information: an online application adapted to different platforms was kept operative from February 2016 to February 2017. Commercial and non-commercial dissemination campaigns represented substantial differences in their success rate and cost-effectiveness. In this study, fisher’s population size, profile and fishing activity were analysed for shore fishing, boat fishing and spearfishing independently in each of Spain’s Autonomous Communities (AC). The official recreational fishing population according to the license registries reported by the AC is of 871,533 fishers, but this study reveals that around 5% of fishers are unlicensed. The most popular modality was shore fishing (83.6% to 67% of recreational fishers) followed by boat-fishing (11% and 31%) and spearfishing (1.2% to 4.9%). The mean age varied significantly between modalities: 36 years for spearfishing, 41 years for shore fishing and 45 years for boat fishing. The education level of spear-fishers and boat-fishers were both higher than that of shore-fishers, which had the highest levels of unemployment. Fisher satisfaction levels of the activity and the catch were high for every modality and AC. Interestingly, a 94% of our respondents declared that their catch was for household consumption. Catch rates differed significantly between fishing modalities: shore fishing had the lowest catch rates (1.17 kg d−1s.e. 0.028), followed by spearfishing (2.02 kg d−1 s.e. 0.044) and boat fishing (2.91 kg d−1 s.e. 0.78). Estimates of annual fishing days (shore fishing 60.6 d y−1 s.e. 0.67; boat fishing 57.1 d y−1 s.e. 0.092; spearfishing 51.5 d y−1 s.e. 0.71) did not differ from those of previously published studies using onsite surveys in the same regions, despite the fact that our sample could be potentially over-representing avid fishers. The implications of misestimating annual effort and its importance on MRF impact are also discussed.