very nice pictures!!! I am impressed, especially that you are not using an external strobe.
Do you have an extra focus light (external) or are you just using your dive lamp? I am having a lot of problems getting the small critters focused with my Canon G9 (also Canon housing). The G9 does not focus well in low light conditions and many pictures are finally blurred or the critters (e.g. Orang Utan Crabs) decided that I have harassed them long enough and crawled into their hiding ...
Well just got a G1X and will also get the housing (canon) for it. Let's see if the situation improves... Just need a macro adapter since the macro ability is not very good.
Anyways, congrats for your pictures, well done!!