What is coal plunging?

The term "coal plunge" does not appear to directly exist in the contexts typically discussed. However, there are references to "cold plunging" or "cold plunges," which might be what you're referring to. If so, cold plunging is a practice involving immersing oneself in cold water. It's known for various health benefits, such as boosting mood, improving sleep, and enhancing resilience to stress.

In one instance, Adam Schafer humorously mentions something akin to "coal plunge" in passing, potentially as a slip or slang for "cold plunge." He uses it while discussing the revival of old training methods and the building of mental toughness 1.

If you meant something different by "coal plunging," please provide more context or check the phrasing so I can assist you more accurately.