One sure way to tell that your dive buddy is narced... he chases fish with his regulator, trying to get them to breathe off of it...*
Narced is a slang term for nitrogen narcosis, a very dangerous and frightening aspect of deep diving.
Narcosis occurs when compressed nitrogen, which is toxic in high quantities, resides in the body of a diver for too long at too great of a depth.
To be narced is to experience feelings of great euphoria, or great paranoia, depending upon the mood of the dive and diver. Most liken this feeling to being high or drunk, which is a very dangerous situation while diving at 100 ft. or more.
Nitrogen narcilepsy, however, can occur at any depth. 100% of all divers who pass the 100ft. mark have tested for some form of narcosis. And in a way, every diver becomes slightly narced as soon as they beging breathing the compressed air.
To be aware of and in control of the effects of nitrogen narcosis is one of the many skills to be had by every diver.
* joke based upon a true story.