Edit:  Ok, I just saw Mark's and its a billion times better than mine!!  Also, I don't seem to have a "Fake Fresnal" option, is that from a plugin?

I don't know about other versions of Carrara but I am using v5 and it come with a bubble shader under the miscelaneous shader section.  I didn't like it though so I modified it a little by adding an alpha channel with a cellular setting.  Also I lowered the reflection alot.  This is what I got.