I recently had a housing flood on my Nauticam NA-D7000 and lost my Nikon 85mm Macro. The camera survived believe it or not. Had it serviced and it checked out. Now I have to buy a new macro lens. If I upgrade to the 105 mm I have to by an extension ring for about $280 and the lens runs about double. So I am in for about $1200 instead of $500.
When I am shooting macro I am mostly shooting with an SMC (super macro converter). If people could weigh in on the advantage in relation to price.