Dr. Mark Harper recalls his first cold-water swim in the south of England 20 years ago. It was August, but the initial jolt from the plunge took his breath away. The shock to his system lasted a ...

FILE - Revelers enter the cold water during the annual Polar Bear Plunge on New Year's Day, Jan. 1, 2025, in New York. (AP Photo/Andres Kudacki, file) (Andres Kudacki ...

Dr. Mark Harper recalls his first cold-water swim in the south of England 20 years ago. It was August, but the initial jolt from the plunge took his breath away. The shock to his system lasted a ...