Just talking about underwater here, but if you're serious about it, then it needs to be a fisheye. The main contender is the tokina 10-17mm FE, but other fisheyes can be used, possibly in conjunction with a 1.4x converter.
Think about the dome port you'll need. There are other options, but the most popular 2 choices are the 4" or 8" domes. For close focus wide angle (CFWA) then you'll be better with the 4" (aka mini dome) which lets you get incredibly close to your subect whilst getting good light from the strobes. You can't quite get as close with the 8" dome but it is slightly more versatile in that it can do split levels much better.
Take a look at Alex Mustards article on amustard.com - I think its titled 'thoughts on mini domes' or something similar.
Rectillinear lenses like the 12-24mm sigma/nikon/tokina variants are quality but will not offer the ultimate close up shots I believe you're after.
Mike