Surf Torture

https://www.yahoo.com/lifestyle/why-people-taking-ice-baths-020000900.html

You're not cold, you just feel cold. Here's a start: finish EVERY shower with a :10 second cold water only phase. It will get easier. Your goal? Work up to a full minute of cold tap water.

https://sgptonline.com/blogs/news/surf-torture-explained-bud-s-training-tips-navy-seal-selection