Wet subjects pose problems due to the highly reflective nature of water. One way to get around it is to use a "cross polarization technique". This entails a polarizing filter on the lense and each of the flashes you use. All the poarizing filters need to be angled correctly to get the desired effect (wet subject, with fewer hot spots from the wet areas).
This technique works very well and is used when photographing not only wet subjects, but other reflective subjects like minerals and gems.
As to macro lenses, I have both Canon EF 100 macros (the old one at home and the new USM one at work). I have also shot with the Tamron MF, Minolta MF & AF as well as the Nikon MF & AF (owned a lot of cameras and lenses over the years). I love the new Canon EF 100 USM - beautiful focusing compared to everything else out there. Optically, these are all comparable. Some of them will not go 1:1 on their own (need extension tubes or converters). One of the huge advantages with the Canons is the ability to use teleconverters (with extension tube), so you can get a 140mm f4 macro (EF 1.4X), and a 200mm f5.6 macro (EF 2X).