is taking over the wellness world. Celebs like and , are hopping on the trend with the best cold plunge tubs. Yep, Americans are purposefully subjecting themselves to a popular form of cryotherapy: submerging in sub-zero waters for a host of alleged health benefits including mood regulation, reducing joint and muscle pain, improving immune system function, and more.“People use cold plunge tubs for a variety of reasons,” says , a board-certified orthopedic surgeon in Baton Rouge, Louisiana, and the founder of .