rapture of the deep 

a mental state or conversational diversion achieved by various technical types when they have become obsessed with an idea that is peripheral (or irrelevant) to the discussion at hand. Commonly experienced in meetings when everyone else is trying to get something accomplished.

Often expanded to infinite rapture of the deep for extra emphasis

Derived from "raptures of the deep" (nitrogen narcosis) that may be experienced by scuba divers when diving at depths below 100 feet.

How'd the meeting go?
--- We were doing well, but then Matt went off into infinite
rapture of the deep about computer languages

rapture of the deep by Golden Rod February 4, 2010