In this paper, an underwater laser cutting process for maintenance and replacement operations is presented and investigated regarding process robustness for the application in rough environments. A Yb:YAG laser is used with 4 kW laser power in an active cutting process with oxygen as cutting gas. For 10 mm thick constructional steel plates a process window is determined with the focus on robustness for distance interferences. The examined parameter sets include the nozzle clearance, focus positioning and cutting gas pressure adjustment, as they are significant factors of influence in underwater laser cutting. By adjusting the developed parameter sets, sheets with thicknesses up to 50 mm, as well as plates that are fixed to a concrete backing are cut. The used equipment, which completely consists of standard components, is presented along with its preparation for underwater operation.