A submerged wave energy point absorber, TWED (Torres Wave Energy Device), has been studied under regular and irregular wave conditions. A partial non-linear time domain model of the TWED has been implemented in Simulink. The numerical model was exploited to test the sensibility of the TWED performance to changes in some variables under regular waves: generator damping constant, floater diameter, depth, frictions and drag coefficients. In this paper, the TWED was also optimized for maximum energy production under a real wave climate. To obtain the average wave performance of the converter, a 44 year series of data record has been employed. The objective functions have been the Average Absorbed Power (AAP) and the sea-state generator damping constant (K). After the optimization, AAP full time series have been obtained. Then several statistics analysis for AAP has been carried out for different time intervals; in order to study the variability of AAP. In addition, an evaluation of the TWED behaviour in a sea state in the Operation Limit has been studied. It has been found that the instantaneous absorbed power in a sea state could be as much as 20 times higher than the mean absorbed power.