There was much to marvel at in this encounter. Once I got past my own personal experience of disorientation I started to reflect upon the swirling phenomenon of the fish: how were they able to move so rapidly and simultaneously? What form of communication could account for their instantaneous changes of speed and motion? I had no answer, though I had seen this same behavior in flocks of chimney swallows and bats—and I am sure there are others. But what about us? Humans. The, theoretically, most evolved creatures on the planet.
My conclusion: The feature in human beings that corresponds most closely to the fish swarm phenomenon is: emotion. Hear me out.
A quote from the Preface to Charles Mackay's Memoirs of Extraordinary Popular Delusions and the Madness of Crowds comes to mind.
In reading the history of nations, we find that, like individuals, they have their whims and their peculiarities; their seasons of excitement and recklessness, when they care not what they do. We find that whole communities suddenly fix their minds upon one object, and go mad in its pursuit; that millions of people become simultaneously impressed with one delusion, and run after it, till their attention is caught by some new folly more captivating than the first. We see one nation suddenly seized, from its highest to its lowest members, with a fierce desire of military glory; another as suddenly becoming crazed upon a religious scruple; and neither of them recovering its senses until it has shed rivers of blood and sowed a harvest of groans and tears, to be reaped by its posterity.Disasters, like those of the Myanmar cyclone and the China earthquake, often draw our attention simultaneously and we automatically respond sympathetically. We saw similar simultaneous outpourings after the fall of the twin towers and after Hurricane Katrina. Max Scheler, German philosopher, identified this simultaneity as what he called a "community of feeling":
"Two parents stand beside the dead body of a beloved child. They feel in common the 'same' sorrow, the 'same' anguish. It is not that A feels this sorrow and B feels it also, and moreover that they both know they are feeling it. No, it is a feeling-in-common, A's sorrow is in no way an 'external' matter for B here, as it is, e.g. for their friend C, who joins them, and commiserates 'with them' or 'upon their sorrow'. On the contrary, they feel it together, in the sense that they feel and experience in common, not only the self-same value-situation, but also the same keenness of emotion in regard to it." The Nature of Sympathy, pp.12-13.Humans are more complex animals than fish or swallows or bats and are capable of more complex, mediated, individual responses. A human emotional response might provoke any of a number or actions—or none at all. However, that doesn't mean there is no emotional response; it just means we don't automatically swarm when we have these simultaneous feelings.
I think it's safe to say that the more significant the cause, the more profound the emotional response, and, thus, the greater the likelihood of a herd/flock/swarm reaction.
[More to follow]