The deepwater hyperbaric GMA welding procedures for sub-sea pipeline repair are evaluated with respect to its behavior under shallow water conditions. In this study, the welding thermal cycles at three different pressure levels were investigated through experiments and simulations. Conventional thermocouple measurements were utilized along with a 2D heat flow model to identify the effect of weld pool shape on the thermal cycle of the weld. A new approach was assumed for considering the effect of third dimension. It was found that increasing the pressure results in minor changes of characteristic weld thermal cycle features. These variations were considered dependent upon the weld pool shape and size. Good agreement was observed between simulated and experimental results.