Colin Smithson was the first to take plunge this morning at the newly reopen Wigton swimming pool.
The pool was closed by Cumbria County Council last year after it was linked to a chemical leak.
Mr Smithson had been one of many people campaigning to keep the baths open.
He said he was "very happy" to be back.
More top news
A look ahead at the forecast for the Border region.
His father, Secretary of State for Scotland David Mundell, is one of the highest profile Remain supporters north of the border.
The company that owns a Cumbrian nursing home has been fined £400,000 after a 91-year-old woman died after falling from her bed.