You may have been seeing this on social media.  It's called "The Cold Water Challenge."  Basically, people challenge friends to jump in cold water this time of year or be forced to pay an amount of money to charity.   A 32 year old father took the challenge, jumped into a body of water and was paralyzed.

While raising money for charity is a good idea, there needs to be some safety measures and proper structure for this.  In this case, it doesn't seem to be the fact that it was cold water that injured the man, but rather a common hazard when diving.  (The bottom.)

However, jumping into frozen lake superior could be deadly if the proper precautions aren't taken.