I am not sure you will get a lot of responses on this thread. FWIW, it is my opinion that the 14-45 is a slightly superior lens than the 14-42 but for underwater use, the differences would be minimal. Either is okay as a general purpose lens, and you can do decent macro with either lens and an adapter and close up lens, but neither is ideal for macro or wide angle. I would suggest deciding which you think is of more appeal (wide angle shots, including close focus wide angle, or macro shots of small things. If the former, look at getting a 7-14, 9-18 or 12mm lens, or my favorite, the 8mm fisheye. If macro, then get the 45 or 60mm macro lenses available for your system. If money is tight, you can do decent macro with what you have now, so I would look at a wide angle lens (unless wide angle is just not your interest. You will need to add a strobe fairly soon as well, although you can do a fair bit of natural light wide angle.
I would make this suggestion, though: Wait until you have been diving for awhile before dealing with the photography. Carrying a camera around complicates buoyancy and task loading at a time when you need to be focusing on diving skills. When you are feeling quite comfortable with your diving skills, then add a camera into the mix. For some this happens fairly fast; for some it takes awhile.
Now a shameless plug: I have a housing and ports for the GF-1 for sale in the classifieds and would be happy to make you a good deal on some or all of what I am selling.
Thank you for the information Moray Eel. Of course I plan to be a good scuba diver first. That's why I want to do a survey first. Since these scuba equipments can be very pricey, I may want to buy the suitable lens or lenses first before getting the housing. I've always wanted to get the 45mm macro but now I've to consider getting a wide lens too. I will let you know on the housing you're letting go after I become a certified diver if it's still available. Btw, is there a link where I can have a look?
I'm sorry I'm posting my enquiries here as I unable to start a new topic.
I'm currently taking lessons to get my OWD cert and hoping I'm able to start scuba very very soon. Surveying what are the options I have for underwater photography. I have Panasonic GF1, G3 and lenses 20mm, 14-45mm and 14-42mm. Thinking of using the GF1 for scuba only
What would be a good casing for GF1 and using which lens? Or would getting a macro 45mm lens better?