Voluntarily lowering yourself into 40-degree water has become a booming business in New York. Cold plunge studios, once the province of professional athletes, are opening across Manhattan and Brooklyn, selling memberships to office workers chasing energy and calm.

The fictional studio Deep Freeze in Chelsea offers guided plunges with a breath coach, timing sessions to the second. Its founder points to a wave of research and louder claims online, though scientists urge caution about the biggest promises.

Believers describe an addictive clarity after the shock wears off. Whether the benefits are physiological or simply the pride of surviving the cold, the studios keep filling — one gasp at a time.