Sometimes heard in military circles, the phrase denotes someone who is overly-involved but doesn't really know what is going involved.
Usually used to point out a
micro-
manager who misses the forest for the
trees.
Upon seeing a clueless officer trying (and failing) to prepare a Rifle-Launched Grappling
Hook for use (not his
job), a soldier might state to another, "Man, the LT is Swimming in the kool-aid, but don't know the flavor."
Variations include "All up in my kool-aid, and don't know the
mix", or the abbreviated "Swimming in it."