The work is to unravel the wave transmission mechanism through modeling the water-filled polycarbonate shell subjected to blast loading. The shock wave propagation inside a shock tube and the interaction between the shock wave and the surrogate head were captured using the arbitrary Euler-Lagrangian coupling method. Results demonstrated a complex fluid field around the head. Pressure history profiles at anterior and posterior sites of the brain simulant exhibited the typical coup and countercoup pattern, which were attributed to the surface pressure wave (direct loading) and the structural wave in the skull simulant (indirect loading). This study could enhance our understanding on blast-induced traumatic brain injury, leading to novel injury mitigation strategies.