It's a new craze which is more dignified than the similar alcohol neck-nomination that swept the nation a few months ago, but nonetheless the Ice Bucket Challenge is not for the faint-hearted and Ana Ivanovic is the latest star to get wet.
Sporting stars, over the last week or so, have been drenched in videos with a bucket of icy water for the ALS charity.
David Beckham, Cristiano Ronaldo and John Terry are some of the biggest names to take the plunge, while Novak Djokovic and Andy Murray are the big names from the tennis world to get a cold shock.
And now the most successful ever racquet player, Roger Federer, is expected to join his fellow pros after being nominated by Ivanovic.
The 26-year-old Russian beauty, who has tried her hand at modelling, displayed her toned abs in her training top ahead of the US Open before being soaked by two helpers.
Before the sharp intake of breath, however, Ivanovic had time to nominate Federer and a few other surprise names.
Serena Williams, winner of 17 Grand Slams, will also have 24 hours to film her own effort. There are clearly some hard feelings from the Russian after Williams defeated her in the final of Cincinnati over the weekend in straight sets.
In another twist, the former world no.1 has also issued Germany's World Cup winner Bastian Schweinsteiger with the freezing challenge. The Bayern Munich star will have to take time out of his busy schedule as the European club football season getting back into full flow.
To be fair, the challenge shouldn't hold too many fears, many of them are forced to take ice baths to help their muscles. Maybe being such a popular sports star does have its drawbacks after all.
There will certainly be some tired bodies at the US Open which starts on Monday. Ivanovic may need to rest her muscles in the coldest possible way if she is to land her first Flushing Meadows crown.
The world no.9 has never passed the quarter-finals in New York and she will hope to add to her major collection six years after her first and only triumph at the French Open.
Somewhat more used to winning in North America are Ivanovic's nominees Federer and Williams. Federer won for five consecutive years between 2004 and 2008, while Serena is the defending champion after bagging her fifth title last year.
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