In general, hydraulic systems that are used for ship fin stabilizers and rudders, are modelled as first or second order of linear equations to obtain only system's delay and overshoot for controlling purposes. This approach assumes the hydraulic system is well designed and contains no faults. It's an easy and quick way to focus on control subject. However, limits and capacities of hydraulic components cannot be examined carefully with this approach. Due to this deficiency, expensive over-engineered or inadequate hydraulic systems can be designed. For this reason, an interdisciplinary study was done in Istanbul Technical University. The purpose of the study is to parametrically model hydraulic system of a ship motion reduction active fin stabilizer system with fins, ship roll dynamics and controllers in detail, so every property of the system can be observed in a simulation environment via non-linear equations. With the help of parametric modelling, every component can be changed and resized easily, including the ship, fins, hydraulic components and controllers. Results obtained from simulation are verified with full scale sea trials using a ship named Volcano71.