For my underwater photography I use Nikon SLR camera's in dedicated underwater housing systems. Up till August 2011 I used a Nikon D80 in a Nexus Housing. I then changed to a Nikon D7000 using a Nauticam NA-D7000 housing.
For lighting my subjects I use two Inon Z240 strobes.
I have a variety of ports to use to accommodate lenses, 60mm and recently acquired 105mm for macro shots. My favourite lens for wide angle is the 10-17mm Fish Eye, but I have also used a 12-24mm.
For topside photography I use both the D80 and D7000 with a variety of lenses and a selection of Lee Filters.