Macro, macro, macro. Bring a macro rig with you to Wakatobi, as you will probably be shooting is most of the time. There are some stunning wide-angle opportunities as well, but the weather prevented us from taking advantage of them.
To shoot some of the smaller critters (like pygmy seahorses), you will need some sort of super-macro setup to allow imaging with greater magnification than 1:1. Most people use teleconverters to do this. A 100mm macro lens with a 2X teleconverter will get you to 2:1, and the addition of extension tubes or diopters will get you even closer. There are active discussions at Wetpixel.com about supermacro setups.
Feel free to bring lots of gear with you. There is plenty of room. :)
Oh yeah. My rig involves Canon, Seacam, Ikelite, INON, and ULCS.