The article presents the results of experimental investigations of interactions between a deformable structure and a liquid. The investigations were performed on two prismatic tanks with elastically deformable top walls. During the investigations, different levels of tank filling with liquid were examined. The investigation of this phenomenon has direct reference to frequently recorded real events, such as collision of a tanker with another ship or a harbour berth, rapid braking of a road or rail tanker, etc. Recognition of this phenomenon is based on simultaneous measurements of the following parameters:
1. excited accelerations of the tank-liquid system,
2. elastic accelerations of top walls of the tank,
3. hydrodynamic pressures on the deformable top walls.