TIL a 30 year diver told me to always pack my own helmet, and it saved my butt on a job in Port Aransas
He said never let anyone else touch your gear because a swapped O-ring will kill you at 120 feet. Sure enough, a tender mixed up my regulator with another guy's and I caught it during the pre-dive check. Anyone else got a rule like that they picked up from an old timer?