Zambezi,
I started playing with photography way back in the 1950's as a teen. So, photographic terms have been part of my life for a long time. I would love to suggest a book on photography basics, but it has been so long since I have had such a book in my mitts, that I just do not know what is out there.
That said, let me be so bold as to suggest you pick up a book on basic photography from your local book monger--or whatever you folks call book sellers. And I would like to suggest you find one of the late Jim Church's book on underwater photography. His or his ex-wife (not widow) Cathy's tomes are good introductions to uw photography although they do not cover some of the idiocyncracies of digital photography. However, basics are basics and I think it will help you master the art.
UW photography is very different from land photography due to the different behavior (behaviour) of light in water compared to air. However, such things as aperature (lens opening), exposure time, depth of focus, effective film speed (ISO), etc. remain the same and need to be understood, even if vaguely.
So, if you can bear to wait a bit before parting with your Krugerands, have a go at reading a few books. If you want to get inspired, you might dig up a book or two by Norbert Wu. He is a master uw photographer who never ceases to inspire me.
Hang in there...and enjoy diving with or without a camera...
joewr