Tunneled planing hull is a special design of high speed craft which can reduce the frictional resistance to achieve higher velocities in high speeds. But, at lower speeds tunnels may lead to increase hull resistance. Therefore, tunneled planing hull design is an important issue which should be conducted with full prior information. In this study, a tunneled planing hull has numerically been studied in details using Star-CCM+ software. These simulations are based on Finite Volume Method (FVM) solution of Reynolds Averaged Navier-Stokes Equations (RANSE). Also, Volume of Fluid (VOF) method has been employed to obtain free surface variations, accurately. Morphing mesh approach has also been implemented to be able to simulate tunneled planing hull in two degrees of freedom in heave and pitch directions. Presented numerical setup has been validated by comparison of computed trim angle and hull resistant against the experimental results which have been presented by previous researchers. Afterwards, various physical phenomena around the considered tunneled planing hull as well as different physical parameters such as skin friction distribution, details of wetted surface area (total wetted surface, tunnel wetted surface, spray angle, keel and chain wetted length), shear and pressure drag, pressure distribution, wake pattern, and stream lines have been discussed, thoroughly. In this paper a new parameter as tunneled efficiency has been introduced based on obtained results. Tunnel efficiency shows appropriate speed range of planing hulls for using tunnel advantages in drag reduction. Presented results help designers to find new insight about the hydrodynamics of tunneled planing hulls.