I do not accept the alcohol analogy. There is almost no similarity. Objective tests conducted on automobile drivers show that one or two drinks of strong spirits actually results in faster reaction times and higher scores navigating the pylons. It's only when consumption exceeds two drinks that scores decline. I personally saw these tests conducted by the police in the DC area about 10 years ago. The results put an end to that particular PR event as I've heard no mention since.
Nitrogen affects a diver in a different way. At the two martini depth a diver is definitely impaired as can be shown by arranged tests such as puzzle solving and reaction times. Typically, the diver will otherwise not be aware of this impairment, as it is relatively slight.
Personally, I have found the following to be true. As mentioned by "100 days", handling and shooting of a speargun is impaired slightly at 130 feet. Same for use of a camera. At 200 feet, it requires concentration to handle and focus a camera. I do not use a gun at this depth as it could be dangerous. My personal limit is 260 feet where the world begins to distort and hallucinate. Frequently, I formed the impression that my fingers had become thick like fat sausages. There is a feeling of being out of control. Unlike alcohol, I never became sleepy or drowsy but it required the same level of willful control as if I had downed two or three water glasses of 100 proof hooch.
I can also state that drinking before diving, even one beer, exacerbates narcosis. This is subtle but can be noticed in the accuracy of using a speargun at moderate depths of 60-80 feet. So, at least in this way, there is some relationship or synergism between alcohol and nitrogen. There is no direct correlation of effects, however, as postulated by Cousteau and some others.