Underwater friction stud welding (FRSW) without a shroud around the stud requires controlling welding parameters to achieve optimal joint strength. A hydraulic FRSW unit has been designed and fabricated to perform FRSW without a shroud via a remotely operated underwater vehicle (ROV). An experimental study has been initiated to investigate the optimal FRSW parameter combinations and corresponding values leading to optimal ultimate tensile load capacity (UTLC) values in the welded joint. The engineering robust design (ERD) approach has been deployed to run the experiment. Each weld has been made with a S355 M12 stud on S355 structural steel plate. This paper discusses the experimental approach, results and conclusions reached in the parameter evaluation, estimation, and experimentation.