AQUASAW C-40 XL
This is the Gryphon AquaSaw, designed for fragging corals with a 42" diamond coated blade. It cuts through corals easily, including serpentine cuts around polyps (Acans, for example).
Use saltwater in the reservoir, not freshwater. 1/4" to 1/2" of water is plenty and avoids excess splashing. Change the water each time you change coral species to avoid contamination or chemical issues that could affect corals adversely.