10 days drinking nothing but water. It's the ultimate challenge of willpower. (And no, you're not even allowed a slice of lemon in it.)
To dramatise just how tough it will be, we imagined ourselves in the pub, standing by the kettle, next to the drinks machine – desperately trying to avoid the drinks we love. All we could hear was the drink talking to us, persuading us to do something bad.
This is what it's going to be like for 10 long days. So we took to social media – we even unveiled our jolly lifeboat singers to step in when the temptation became overwhelming for some.
Nearly 7,000 people signed up to take part, 90% of them brand new RNLI supporters. In total, we raised £174,000 – and we're doing it again in 2016.