Matutano, C.; Negro, V.; López-Gutiérrez, J.S., and Esteban, M.D., 2016. Hydrodynamic regimes in offshore wind farms. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 892–896. Coconut Creek (Florida), ISSN 0749-0208.Offshore wind power has sharply increased its presence in the last few decades. This expansion has derived in much bigger structures to be placed on the seabed; however, no revision about hydrodynamic regimes that should be taken into account during the design of these facilities has been carried out. The equations developed by Morison et al. in 1950 to estimate the wave loads are commonly assumed as valid within professional and scientific activity, and no revision of their investigation has been carried out since then. The formulation developed 65 years ago may not be reliable enough to accurately predict the phenomena, since they were established for smaller bodies. This paper analyses the available data from several European offshore wind farms in order to determine their hydrodynamic domain and nature of forces that structures bear. The analysis has been performed with the aim of establishing the relationship between inertia and drag forces acting on piles under wave loading conditions. Different criteria from main standards within the sphere of maritime works have been followed for the analysis. Results clearly show how inertia dominates in most cases and, consequently, the acceleration of fluid particle motion is a critical variable for predicting coastal phenomena. In this sense, this research remarks the importance of that mathematical expressions incorporate this fact, both for structural calculation and coastal process prediction and they should be reviewed in future research studies.