A diver from Leyland, Lancashire, is challenging the world record for the longest time spent under water.
The previous underwater world record stands at eight days
A special tank has been delivered to a warehouse near 35-year-old Mark Webber's home in preparation for the bid later this year.
He hopes to raise thousands of pounds for charity by breaking the current world record which stands at just over eight days.
He will sleep underwater and have his air replaced at regular intervals.
Noughts and crosses
Extensive tests will be carried out on the tank and equipment, which includes a bed, before the record attempt.
Mr Webber will wear a full-face mask during the attempt and have his air supply replenished at four-hour intervals.
He will pass the time playing noughts and crosses with visitors, using the side of the tank as a makeshift pad.
Fellow divers will also join him in the water for games of chess, say organisers.
The father-of-one said: "I'm hoping to spend 15 days in the tank if I can.
"I've spent eight years putting together the plans to do this and I'm really determined."