I've been using my Nikon D7000 with a Nikkor 60mm macro lens in a Sea&Sea housing since 2013 and lately gotten more and more into super macro (hairy shrimps, skeleton shrimps etc.). I have two INON UCL-165 (screw on), but still have to crop more than I would like if I take a picture of something like a Costasiella kuroshimae (Sheep nudibranch) and the depth of field gets ridiculous. I'm wondering what kind of options I have in upgrading my system. Would it be wiser to go with
a) stronger wet lenses
c) extension tube
or do I have other options? What are the pros and cons? If I can get better magnification and better depth of field I'm prepared to invest in a 105mm lens and extra housing parts as well. I'd love to get some extra working distance between me and my subjects as with both wet lenses on the subject is pretty much attached to the glass. I've attached some pictures just to show my cropping issue even though the order became messed up (pic 1 and 3 are from the same picture).