As a former Design Engineer at Newport News Shipbuilding I worked extensively with titanium alloys in the design of submarine components. Titanium is an excellent material for a number of reasons and is especially well suited to a marine environment because of it's corrososion resistance and strength.
Some time back the Russian navy produced a class of subs with a titanium hull. They were welded in a large inert gas filled chamber with welders in moon suit like gear and oxygen supplied through hoses. The issue at the time as far as my understanding goes was that in order to prevent contamination of the weld material the hot weld must be shielded with argon gas until the weld is below around 650 degrees F.
Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.