A watering hole, in English slang, is generally a local bar or pub -- somewhere where everybody knows your name, and a few good times can be had over a few good pints.
Watering holes must serve draft beer; bottles don't cut it.
The American Heritage Dictionary of the English Language defines a watering hole as:
1) A small natural depression in which water collects, especially a pool where animals come to drink.
2) A social gathering place, such as a bar or saloon, where drinks are served: “a Warsaw restaurant that was once a cosmopolitan watering hole for actors and writers” (Newsweek).
An essential part of the cycle of life, watering holes are fraught with danger. They are never the innocent, idyllic pool of "the water of life" that they are made out to be. One must learn to take the better with the bitter. While many creatures rely on them as a source of health and mirth, they are a draw for predators. Danger lurks in the shadows.
Sip your drink carefully, my friends. Nothing is more vulnerable than a thirsty vegetarian.