Despite what was said in "The Waterboy," anger and aggression is not controlled by the medulla oblongata . This is the job of the amygdala. In the brain, as soon as an aggression starts, our alarm system, the amygdala, is activated and this triggers a cascade of reactions to prepare our flight.
In one recent case, after a near drowning incident, I could not only vividly remember each detail, but while doing this, my body reacted as though I was reliving the experience. I was immobilized and unable to escape fast enough, the amygdala panics, and is flooded by alert signals. The amygdala "overheats," and suddenly I was unable to defend myself. I was paralyzed and felt like I was going to die. The time of the drowning is trapped as such in the amygdala. Maybe this is why I no longer swim alone?
I enjoyed the comparisons you made between the amygdala and an arm clock. It is really interesting how the amygdala seems to "wake up" during certain life events and goes into a sort of hibernation at other times. I'm fearful of the water too, so I can relate to this!