This paper describes the innovative offshore point-absorber wave energy converter (WEC), IRWEC1, under development by the Hydrodynamics, Acoustics and Marine propulsion Group at Babol Noshirvani University of Technology. Totally enclosed in an outer shell, with no external moving parts, IRWEC1 is completely sealed which make it a robust and trustable system. Important motion for this WEC is the pitch motion, so, a pendulum is designed for transferring this motion to the PTO. In this paper, the WEC is evaluated for a wide range of waves in the wave tank. The wave characteristics are presented by which the system had appropriate pitch motion and acceptable extracted electrical energy.