Since June, several thousand people worldwide have recorded themselves getting drenched, then posted the stunt online and challenged others to do the same, or pledge USD 100 to ALS research.
Many have done both, in an effort has raise millions of dollars for the ALS Association, which combats amyotrophic lateral sclerosis, also known as Lou Gehrig's disease.
Some 30,000 Americans have ALS, which attacks the nervous system and eventually leaves victims paralysed.
Politicians and sports figures went at it too, including New Jersey Governor Chris Christie and basketball superstar LeBron James.
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Bare-chested English footballer David Beckham got in on the act, as did World Cup stars Neymar of Brazil and Argentina's Lionel Messi.
Normally reserved former US Federal Reserve chairman Alan Greenspan can be seen gleefully dumping ice water over his wife, MSNBC anchor Andrea Mitchell.
Ethel Kennedy, the 86-year-old widow of senator Robert Kennedy, doused herself and challenged President Barack Obama to do the same. The world's most powerful man declined but promised a donation, according to the White House.
The charitable challenge's popularity has spread around the globe in recent days, particularly to Britain, Australia, New Zealand, Canada and Germany.
Facebook said that between June 1 and August 17 more than 28 million people mentioned the challenge on the social network, and 2.4 million videos were posted.