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The use of underwater wet welding for offshore repairs has been limited mainly because of porosity in the resulting welds. With the appropriate consumable design, however, it is possible to enhance weld metal toughness and reduce porosity. This WRC Bulletin examines the use of titanium- and boron-based consumables developed to produce high-toughness acicular ferrite. The presence of titanium resulted in the formation of inclusions which assisted the formation of acicular ferrite and countered the rapid quenching effect of the underwater environment; boron additions decreased the amount of grain boundary ferrite, further improving the microstructure. It is shown that the weld metal titanium and boron compositional ranges for acicular ferrite maximization varied with the heat input and the cooling rate. Publication of this document - WRC Bulletin No. 399 was sponsored by the Welding Research Council