<font color='#0000FF'>Hi,
I gave up a couple of years ago with the help of Zyban but I started again about a month after stopping the course of tablets. I didn't dive on zyban so can't comment on it's underwater effects. The tablets made me feel a bit 'happy' and a little spaced out. I personally wouldn't dive on them.
As Steve has said, you must have a solid reason to quit (other than death from a smoking related illness 'cause that's not normally 'good' enough).
I gave up for good in January because smoking and DIR don't mix. GUE won't entertain smokers and I had a course to do. That was a good enough reason for me
I used nicorette gum this time and it worked just fine.
Good luck (not that you'll need it on zyban - it works)
Mark