Any comments greatly appreciated....
Pete in sunny (but chilly) Florida.
Hi Pete,
I don't use the A80 but a friend of mine bought one and got excellent results with the internal flash and the diffuser. All the pictures were taken in Auto and Macro mode. He got very nice pictures of anemones. Of course pictures taken at more than two feet were full of particules but the close-up were gorgeous.
You don't have to be concerned about bringing your A80 with it's case in your "chilly" Florida waters because my friend took his pictures in 30F (-1C) water. Yes I know it's bellow water freezing point but it is salt water! The outside temperature was a "balmy" 14F (-10C). B)
If you want to have a look at my home page you will see some examples of what can be done with the little brother A70 and some tips for ambient light photography. I suggest you try to take your pictures at ISO 50, this is what gave me the best results.
I could add do a "custom white balance" when you're not using the flash.
Turn off the Red eye reduction lamp when shooting fish or light sensitive subjects (christmass tree worms) don't use the Af-assist-beam either.
You should also consider adding an external strobe in the future.
Hope this helps.