The manuscript analyzes the impact of a non-contact underwater explosion on the foundation of a 35 mm naval cannon mounted on board a Project 258 minehunter. The finite element method was used to complete the task. Cole's empirical formulas were used to describe the distribution of the pressure wave from the explosion of the TNT charge in water as a function of distance, time, and mass. The hull geometry was reflected based on technical documentation as a shell structure reinforced with beam-bar elements. Devices with large weights were represented as rigid bodies. Simplifications were used to minimize the number of degrees of freedom. The construction of ship's hull is made of non-magnetic austenitic steel. The dynamic characteristics of this steel were determined based on static and dynamic tensile tests. The Johnson-Cook constitutive model was used to describe the material properties of steel. As part of the work, the impact resistance study of marine structures was presented, how it is defined by the existing regulations in the Polish Navy was considered, and the scope of their applicability was given. The scientific innovation of the presented work consists of checking and specifying the guidelines for designing and constructing warships.