SWIM (3)

Swim, n. 1. 1. The act of swimming; a gliding motion, like that of one swimming. B. Jonson.
2. 2. The sound, or air bladder, of a fish.
3. 3. A part of a stream much frequented by fish.
Swim bladder, an air bladder of a fish. — To be in the swim, to be in a favored position; to be associated with others in active affairs.