What are the pictures you want? Macro is more than possible, you can get very good shots with one strobe, though many shooters still prefer two for more lighting options. True wide angle is generally not possible as no strobe has the coverage for it. CFWA, where you balance a strobe lit (small) subject in the foreground with an ambient background, could be possible once you figure it out.
Is it crazy? As long as you have the means, only you can tell. My gear is a bargain for the ~100 dives I do in a year, but if I only could do 10 dives a year then I might rethink it.