I can't immediately think of any really scary thing....
But as a little un occasionally we would go over to Stourport-on-Severn...
there was, (and still is), a cheap tacky amusement arcade, Bumper-cars & tall slide close to the rivers edge...
and a cast iron open spiral staircase footpath from the road down to another path by the side of the river...
A few of these used to give my the craps thinking I would end up in the river...
Dekerington (AKA Spark Of the Year).. may have been over as its not far from him either...
Pictures help so here goes..
exhibit A.
Green dot= Swing footbridge, (used to be narrower)...
Red dot= High slide.. side nearest the river was the poo your pants side...
Blue dot= Bumper Cars.. Don't crash cars on the side near the water as you may shoot over the barrier into the dock!
Yellow dot= Open cast iron spiral staircase... look down through the stair tread and see the river just to the side....
or from a different angle..
exhibit B..
it must have been some subconscious fear of falling in the river....
but when you are little the river always looked MASSIVE and the gaps you could fall though seemed guaranteed to catch you out!!!