When scuba diving, try not to wear a sombrero. While it may seem like a good idea on the surface, in the water it is a whole different kettle of piranhas. First, air bubbles collect in the top, making the hat bouyant. This has the adverse effect of making the string attaching the hat to your neck into a kind of cheesewire, cutting into your throat. Second, the hat rim will get in front of your eyes, making it impossible to see who is attacking you, in the invariable fancy dress underwater fight that will occur. Third, it scares the fish.