ducks on the pond

Meanings

1. A coded warning used by men to alert each other that female guests ("ducks") are present ("on the pond"), so that for politeness they should moderate their language.
2. Members of a batting order who are on base; baserunners.
3. There are customers arriving on the car lot.

Etymology

* (coded warning): Originally used in shearing sheds; later extended to other normally all-male environments, such as some pubs.