Foster was a six-time world champion and he won two Commonwealth Games gold medals and 11 European titles.
Now a pundit and a presenter, he told BBC Essex’s Breakfast Show that swimming was a unique sport because “it is just you and the water”.
“When people are at the gym or go for a run, they are always tapped into something,” he said.
“Nowadays, everybody is just overloaded with stuff, whether it is emails, social media or calls.
“It is really important to unplug yourself and take yourself away from it – whatever it is – and that is the beauty of swimming.”
In The Thousand Mile Challenge, each team member will swim 24 miles between Monday, 4 November, and Friday, 8 November.
In a 25m pool, 24 miles equates to 1,545 lengths.
The Essex team also includes Breakfast producer Lois Worrow, sports journalist James Patient and news editor Claire Sawyer.
Foster said he had noticed how diverse people he had seen swimming in his native Essex were in terms of age and sex.
“I find it really inspiring and really good that there are people unplugging themselves from the way the world is moving – and it is going very quickly,” he said.
“If I had advice for anybody it would be, ‘Put your phone down more often’.”