Water hammer problem in a complex geometry critical pipeline is going to be considered. Advanced simulation of a 3D dynamic model is going to be performed with the aim of determination of mechanical response of the support system for the pipeline attached to the submerged tunnel walls. Water hammer phenomenon is going to be considered as a main mechanical load for the structure. The pipeline being critical with the reference to risk of failure is under consideration of rapid toss in case of loss of, i.e. voltage spike or other reason.