Since it seems to be digital photography week...

Does anyone have any tips, or is there an idiots guide anywhere to
tweaking underwater pics in photoshop (or similar)to correct colour
balance (specifically the very blue casts I got a year or two back in
the red sea when using a digital camera at anything more than 10 or so
meters down without an external strobe).

I've never really spent much time in photoshop, but when I have tried
randomly moving red and blue and green sliders about, it doesn't
really seem to achieve what I am looking for.

I did try a plug in filter (Digital ROC from memory?) which seemed to
do the right sort of thing, but I suspect that with a little bit more
knowledge, it would b possible to produce better results manually.

David