I think your getting caught up with the whole true macro way of thinking.
True macro lenses are able to capture an object on the camera's sensor at the same size as the actual object (termed a 1:1 or 1.0X macro). Strictly speaking, a lens is categorized as a "macro lens" only if it can achieve this 1:1 magnification.
Your right to get 1:1 magnifaction you need to be 48mm away from the subject with the 60mm, 145mm away with the 85mm, and 154mm away with the 105mm. This is only to get 1:1 image size.
In its purist form macro photography is getting that 1:1 image size but honestly the macro term is loosely used for any close up photography which has higher magnification than 1:1. So most of the "Macro" shots you see are actually not True macro but a close up shot of the subject.
The 60mm Nikkor macro is one of the most common and widely used macro lenses due to a number of reason. Its versatility, ease of use, and cost make it most often the first choice of lens for underwater close up work. Most often the 60mm will do what is required for close up work on subjects which are not shy or move quickly ie Nudibranchs, slow moving shrimps and crabs, soft corals etc etc. For those than shoot more shy subjects which are hard to get close too like gobies for example, use 105mm with its extra focal length.
Ikelite do not have 67mm thread on their dedicated ports so if you want to go for the Subsee you will need its holder which comes at a cost often more than a lens.
For first time underwater Macro (close up) photographers I suggest you start off with the 60mm Macro (even the older AF-D) as its cheaper. Once you have mastered the 60mm and need more focal length then go for the 105mm. The 85mm is a DX lens and maybe the next camera you buy after the D7000 will be full frame so my advice is to keep away from DX macro lenses and stick with the tried and proven 60mm or 105mm lens.
Another option and also a cheaper one is that you buy the Nikkon 60mm AFD lens and use a teleconverter like the Kenko pro 300 1.4X. If you add this to the 60mm you turn it into a 84mm focal length but with an image size of 1.4x.........all you need is to find a port to fit it in and from memory it fits in the dedicated ikelite 105mm port.
- bgfspeedy likes this