Filmed on his yacht, the X Factorjudge can't stop giggling as he awaits being soaked in freezing water.
The businessman nominated his fellow judges Louis Walsh, Cheryl Fernandez-Versini and Mel B to complete the challenge within 24 hours.
The challenge aims to raise awareness for ALS (amyotrophic lateral sclerosis, or motor neurone disease), a terminal illness that weakens and stiffens muscles. The challenge involves people having a bucket of freezing water poured over them, while also nominating others to follow suit.