Scuba diving is an incredibly safe sport, but we are still humans exploring an alien environment. Sometimes, things go wrong. A mask strap snaps, a regulator starts to free-flow, or you temporarily lose sight of your buddy. In these moments, the actual problem is rarely what hurts a diver—it is the mental reaction to the problem. Panic is the ultimate underwater enemy. Here is how dive professionals train their brains to override the fight-or-flight response and stay completely calm when a dive goes sideways.