What camera, housing and port are you takling about Ron? There are a huge number of variables in the scenario but here's a stab at it:
CC fiter: Off (or your lights will turn the coral red)
White balance: Preferably manual white balance on something white illuminated by your lights at the same range as most of your coral will be. Alternatively see how automatic white balance goes, or even an "outdoor" preset.
Iris: I reckon about F7-F8 would be good for this. You want to avoid a large iris like F2 which will reduce the depth of field, or a very small iris like F11 which can give distortion.
Gain: 0dB (shouldn't need any gain if you're looking up towards the light)
ND filter: Normally off unless the camera is calling for it. You might bring it in before the camera calls for it if the iris gets really small, like smaller than F8. But bringing in the ND filter will widen the iris and so reduce the depth of field, which is not something you want if your coral and distant diver are both to be in focus. Looking towards a bright sun there's a good chance you'll need the ND filter.
Shutter speed: probably 1/50 if you're shooting 50i or 1/60 if you're shooting 1/50. If you have too much light and your iris gets to the really high numbers you could speed it up but like the ND filter that will widen the iris.
Lights: This depends on how much coral you want to illuminate. If you're looking twards a bright surface then you'll need a lot of light to keep up with it, otherwise the coral will just be dark. I think halogens would struggle. HID is normally much brighter than halogen and there are even brighter lighting technologies around now. Also bear in mind halogens are less matched to daylight and give out a redder light.
You may well need to blue up the water in post as it could come out a bit washed-out turquoise.