In conventional stick electrodes it is possible to add ingredients basically only in the external covering. A tubular covered electrode (TCE) allows the addition of reactive elements in the hollow rod, separate from the other ingredients used in the flux covering. This paper describes the underwater wet welding (UWW) TCE application with exothermic additions and its influence in the weld metal composition and porosity.  Tubular covered electrodes (4 mm external tube diameter with 1mm wall thickness) with a commercial E6013 external flux layer and seven different internal flux compositions (100% iron powder, 90% Fe+10%Al, 80% Fe+20%Al, 50% Fe+50%Al, 90% Fe+10% CaC₂, 70% Fe+30% CaC₂, 20% Fe+80% CaC₂) were used to make bead-on-plate (BOP) welds. At least three BOP welds were made with each electrode composition on 12.7 x 25.4 x 250 mm A36 steels plates at 50 m water depth using a gravity feeding system inside a hyperbaric chamber filled with fresh water. The same current value for each electrode type with direct current electrode positive (DCEP) was used.  The results shown that Aluminum and calcium oxidation reduced porosity formation in underwater wet welding through decreasing CO and droplet size. At high concentrations, greater than 20% addition in the internal fluxes, aluminum also protected the transfer of alloying elements such as manganese and silicon. Calcium carbide additions increased weld metal carbon content, produced short and more stable arc, and helped to protect the transfer of important alloying elements.  These results confirmed that TCE application in UWW is good alternative to control the weld metal chemical composition, porosity and microstructure.