Another advantage is not needing good visibility to get great shots. A macro lens is usually defined as a one to one lens.
This relates to the old 35mm negative and slide film days when the size of the subject was life size on the film. If the subjects were enlarged anymore on the film it could be termed super macro. In the digital age sensor size is largely irrelevant for super macro although a larger sensor and higher resolution will allow images to be cropped better.
For any form of macro a good strobe is a must, shooting that close to your subject gives very little depth of field so using the highest aperture setting on your camera is essential. Placing the camera that close to the subject also blocks available light and accentuates the need for a strobe.
I generally find that one strobe is adequate for super macro, its positioning dictated by the subject and the terrain. Use of two strobes often makes getting into the nooks and crannies difficult. On compact cameras a supplementary close up lens can be stacked (doubled up) to get results. On an SLR you have the choice of teleconverters, extension tubes and dioptres. You can even use all of them together. On my SLR set up with all three of the previously mentioned I can focus down to subjects the size of a grain of rice.
The hermit crab in the olive shell photograph in this article is about the size of a baked bean. Some camera housings will also take a wet lens that can be placed in front of the camera housing port and be added or removed underwater as required. One accessory that is very handy is a good aiming light so your view while composing the shot is sharp as being that close blocks out most surrounding light. The use of extension tubes teleconverters etc all cause a loss of light reaching the sensor so a strobe with variable power output is a good investment. All these images were taken at Jones Bay, Tawharanui, New Zealand, which as any local knows, never gets good visibility.