Had to laugh when I read the thread post up and what followed. Years ago, if I fell in, I'd sink like a rock I swear to God. Now? A fly box not much bigger than a pack of smokes in one pocket, two spools of leader material in another and a small string of 'tools' clipped to my shirt front by a set of 'hemostats' used as a hook remover. Strong preference they be used to remove the fly from them ... not me.
That all aside, the one thing that folks don't have on them is a good Police Whistle (mines on the end of that Hemo cord tool kit noted above). You have a problem, you're out of cell phone range (or its soaking wet and doesn't work) and in deep do-do. No one
will ever hear you call for 'help.'
The sound of a whistle, that (and the Universal three blasts) can be heard one hell of a long way off. Even over the noise of a boat motor.
A good thing me thinks.