Wet welding with covered electrodes (Shielded Metal Arc Welding-SMAW) is the most commonly used method of carrying out welding repair works in a water environment. Limited visibility and the inability to move freely under water result in an increased risk of formation of welding imperfections such as lack of fusion, lack of penetration and arc strikes. The work focused on changes in the properties and structure of steel subjected to the impact of short (0.2 s) arc ignitions generated by covered electrodes in air and under water for three high strength steel grades: S460N, S460M and S500MC. Visual tests, macroscopic and microscopic metallographic tests, microhardness measurements and diffusible hydrogen content in deposited metal determination were performed. A significant influence of the environment on changes in the morphology and microhardness of steel in the vicinity of arc strikes was found. The microhardness of the areas covered by the rapid thermal cycle caused by SMAW increased from 200-230 HV0.5 to 400-500 HV0.5 depending on the steel grade. The presence of welding imperfections: cavities and cracks were detected. The susceptibility of all steel grades subjected to short thermal cycles to cracking was confirmed by the results of measurements of the diffusible hydrogen content: 38.6 ml/100g and 84.5 ml/100 g for air and water environment, respectively. No influence of changes in the welding current on the behavior of the material in the tested conditions was found. The conducted research shows that leaving arc strikes on the structure may have serious consequences and cause a failure.