The 83-year-old ex-paratrooper has been as regular at the in 'Dip with a Nip' at Prestwick on Boxing Day since it began in 2006.
And this year will be no different.
He said: "You get a shock when you hit the water that's six degrees below freezing but I always look forward it."
Bill from Braes-O-Yetts, in Kirkintilloch, fights the winter waves to raise money for the CLIC Sargent children's charity.
The charity has branched out to five locations around Scotland because the event was such a success. Prestwick attracts the largest crowds raising thousands of pounds each year.
Fundraising manger for CLIC Sargent, May Gilchrist, is delighted the event attracts so many people.
She said: "It is such a silly idea and become really popular so now it's part of the social calendar.
"Bill is a hardy guy. One year I came down wrapped up before the event and he was already there in his speedos on the beach ready to go because he was planning to watch the football later."
After 18 years of military service and two replacement knees, Bill continues to keep in shape by going to the gym three times a week.
He said: "I like to challenge myself and stay active."
Lollipop man Bill has also taken part in the New Year's Day dip in the Gare Loch, near Helensburgh, for the last 15 years to raise money for the Lifeboat Fund.