Back in August 2015 I answered a Writer's Block question about unusual experiences; one of mine was something I promised to tell on request, but then I couldn't get on-line.
Once upon a time I went on holiday to Saint Ives, Cornwall. It's a beautiful town by the sea. As far as I can remember I was staying with a friend of my mother's, to recover from ... something. I was a young teen; perhaps 13.
I loved the sea there. I used to float quietly and watch the fauna going about their lives. There were two beaches - I think it was Portmere for surf and danger. Portminster was the safe one, with chest-high water for a long way out, before a drop-off that led to the depths.
I was sensible and stuck to the safe beach. The sea was pure, apparently non-polluted and almost as clear as air; I could bask on the surface like a seal, watching the wildlife below through the water. (By hindsight I did almost everything wrong, but I had no idea of some of the risks.) I loved the peace and tranquility and started going out to swim in the early morning.
On the day it happened a family had the same idea and four or five young boys and two adults were threshing the water white about 30 yards away, also on the edge of the drop-off.
When I dropped into my usual easy float I realised that all the fish had gone. The seabed under me seemed empty. That was odd, the fish and crabs weren't usually bothered by a noise at a distance. When I stood up I realised that the seagulls were missing, too. Furthermore, it was me they seemed to be afraid of! There were no gulls for a very wide circle around me, although there were some beyond the noisy family.
I slowly looked around, turning until I was facing out to sea - and then I looked down.
There was a long, dark torpedo shape just beyond the edge of the drop-off, with its broad snout towards me. Focused on me. I think it was less than its own body length away from me, deep enough so the fin didn't break the surface. (Maybe two yards long and and four or five feet away? Difficult to judge, because it was also down at about shin level. I only had a split second glance at it ...)
I screamed "SHARK!!!" at the top of my voice and jumped! my first leap must have taken me almost clear of the chest-deep water but there was nothing to jump onto; I was twisting around to face the beach at the same time and I probably came down almost at my take-off point.
I almost fell when my foot landed on what I thought was a big rock, but I kicked off from that instantly and jumped again and again...zigzagging to safety leaping like a frantic kangaroo, probably shrieking all the way.
When I got the beach I half expected to be scolded as a stupid kid, play-acting for attention.
That didn't happen. Everyone who looked up at the first shriek had seen the rear end of the shark's body come out of the water behind me! I was told that it then swam away at full speed, also in a frantic zig-zag at the surface - and it was also apparently trying to get out of the water!
Now, of course, I know more. Don't swim from a drop-off, don't wear a (school regulation) black swimsuit, don't swim quietly at a distance from a party who are making a lot of noise (that can attract in predators who then hunt stragglers). Don't swim at dawn or dusk, don't get mistaken for a seal, don't ...
I've kept tropical fish for years. Fish hear by vibrations in the water and it's possible that the fuss I made was enough to terrify a shark - but zig-zagging on the surface is the way a fish tries to escape something big and dangerous coming at it from underneath. Fish also do that when injured.
I've also read that sharks don't particularly want to eat humans. They check out a potential dinner, zero in for an "investigatory bite," shake the victim if they can, back off and then take their meal once it bleeds out. (Unfortunately that investigation is enough to kill or maim a human.)
I remember that part of the drop-off, and the shark beyond it, with photographic clarity. There weren't any big rocks there, I'd have noticed. (The ecology around a large rock is is interesting and different.) I don't think there were any big rocks near the edge of the drop-off at all, the tide saw to that.
The shark had been watching me; I suspect that at first I'd looked something like a seal, then I'd turned vertical and started to move incomprehensibly so it charged in fast for an investigatory bite, to see if it liked me - and in that same split second I'd jumped straight up! (Which fish don't do.)
Creatures that charge at prey have momentum.
I suspect that it started to pass under me a second after I jumped - and when I came down, very hard, I almost fell when one foot landed on its snout! I bounced straight into another leap - which slammed its relatively sensitive snout between my heel and the bottom at least once, probably twice.
If I'd landed on its eye or gills I might have disabled it, but the snout would have been quite bad enough, from the shark's viewpoint.
Given a shark's likely experience, the only thing it could have thought was that something huge had bitten it. (The shark's zig-zag retreat and mine seem to have mirrored each other - probably for the same reason; "It's coming after me! It's down there with teeth!! Gotta get away!!!"
Anyway, to avoid shark attack, don't bathe from drop-offs, don't wear black and white, don't float quietly near an uproar ...
and if the big scunners bother ye anyways just gie 'em a damn good kicking!