Maybe you've seen the news on Mayor Rahm Emanuel and comedian Jimmy Fallon taking the "polar plunge" in Lake Michigan. How brave! How freeeeezing!
Mary Baker Eddy talks about another plunge – the mental plunge Jesus took – on page 313 of her book Science and Health with Key to the Scriptures:
Jesus of Nazareth was the most scientific man that ever trod the globe. He plunged beneath the material surface of things, and found the spiritual cause.
Jesus taught that God, the one Spirit, made us in His own image and likeness, contrary to all surface appearances. Then he proved, by his fantastic healings, that we are spiritual and perfect, not material. This was indeed a brave plunge taken in behalf of all God's children everywhere!