Michael Garrett and Ryan Duey of Plunge say their cold tub -- set to 55 degrees -- tackles inflammation and more. Robert Herjavec agrees to give it a shot, and the rest of the Sharks get a big laugh out of his screaming as he adjusts to the cold temps. From 'Shark Tank' season 13, episode 21. Watch 'Shark Tank' FRIDAYS 8/7c on ABC. Stream on Hulu.