Viscous drag forces in mathematical models for wave energy converters are usually modelled by means of a term based on the Morison equation. Due to large relative velocities, induced by control strategies in order to increase the power absorption,viscous losses can have a high impact on the model accuracy and,in turn, on the model-based power optimization control strategies.Notwithstanding the importance of a reliable estimation of the drag coefficient in the Morison equation, much inconsistency and low trustworthiness is found in the literature, about both the values themselves, and the identification methods.Indeed, drag identification for wave energy applications is particularly challenging, mainly due to the device dimensions,characteristic flow regimes, large motions and, in particular, the presence of the free surface. An ideal identification test would be able to replicate the full complexity of the flow, and concurrently to isolate viscous forces from other forces and nonlinear effects.This paper seeks to discuss the inherent challenges to drag identification, proper to wave energy applications. Moreover,different identification techniques are implemented, evaluated and compared, with regard to the estimation of the drag coefficient for a floating heaving point absorber.