When I in my teens, we were at Nagshead, at the beach when my youngest brother started yelling "Shark!". Dozens of people started yelling "Shark!" and running up the beach, far from the water, like the sharks were going to land and come up the beach after them. I looked at the half dozen or so, large, gray, fish like creatures and yelled "They are dolphins!". The whole crowd, enmasse, started yelling " Dolphins!!!", ran back down the beach, charged into the water and started swimming towards the dolphins. The dolphins rapidly fled. It was one of the stranger things I have ever seen.

People went from terrified to jubilant in seconds.

Keith