“One study showed significant and prolonged increases in dopamine when people were in cool (60°F) water for about an hour up to their neck, with their head above water. Other studies describe significant increases in epinephrine from just 20 seconds in very cold water (~40°F). The good news is that as you do deliberate cold exposure more often, you will be more comfortable in the cold at all times and can start to use colder temperatures with more confidence, just like exercise.” Dr. Andrew Huberman