Dynamic response of a round aluminium tube supported at both ends was investigated when impacted at its centre by an external mechanical loading. The tube was subjected to different conditions. First, the empty tube was tested. Then the tube was filled with different amounts of stationary water (i. e. 25%, 50%, 75% and 100% full), based on the inner volume of the tube. Finally, flowing water through the tube was considered. Different magnitudes of impact loading were also applied. The study was primarily conducted experimentally with some additional numerical studies completed to further understand the results. The impact force, as well as strain along the tube, were measured for all described test conditions.