Alan Jackson, from Wells, will be 75 when he attempts to swim the 21-mile stretch between England and France as part of a relay team next week.
There are five men, including Mr Jackson, in the team and they are all 70-plus with a combined age of 370.
If the five men make it across to the French shoreline, they will be the first team of swimmers aged over 70 to conquer the gruelling swim.