What is a part of a stream much frequented by fish. [Eng.] 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. [Colloq.] called?

swim — A part of a stream much frequented by fish. [Eng.] 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. [Colloq.]. (Webster's 1913.)