It is not a good a idea to drink and dive, no pun intended. If you go deep you might puke into your regulator.
I copied this text from a dive site. The text is written by a doctor and addresses the issue of drinking and diving. Please take heed from the warnings, I once drank a bunch of beers and went diving, threw up under water and almost drowned. Dive sober.
Aside from the medical problems that may occur, a diver must keep his or her wits about at all times. Otherwise you may endanger yourself or your dive buddy, consider the latter next time you want to pop open a beer before a dive.
Sorry for the lecture.