bajar al pozo

In mining contexts, bajar al pozo literally means to go down into the mine shaft — a routine phrase in mining regions for miners starting their shift underground. In some colloquial registers it's also used as a crude euphemism, so context matters for which sense is meant.

• Los mineros bajan al pozo antes del amanecer. — The miners go down into the shaft before dawn.
• Trabajó veinte años bajando al pozo todos los días. — He spent twenty years going down into the mine every day.
• El accidente ocurrió justo cuando iban a bajar al pozo. — The accident happened right as they were about to go down the shaft.

Outside a clear mining context, the phrase can carry a crude euphemistic meaning in some dialects — stick to the literal mining sense only when the topic is clearly about mine work, and otherwise avoid the phrase to sidestep ambiguity.