Check the vendor ratings very carefully before purchasing online and from mail order camera sellers.
There have been a lot of stories of wrong power chargers (Oz uses a different plug type), foreign language menus, etc. etc. and a lot of headaches.
For cameras, you are probably better off buying locally so you can get the support and warranty.
A lot of people inquire about purchasing the latest and greatest cameras from Japan but I have to turn them away due to the language issues, for example the manuals and onscreen menus are in Japanese, etc.
For purchasing online, I recommend B&H or Adorama in order to not get ripped off. They have higher prices but are much more reputable than most other mail order places. See "Where to buy a camera" on photo.net.
Also, I suggest supporting (your local) specialized dealer of underwater cameras/housings so you can get some feedback and instruction.
Good luck,