When you see two fins coming at a pair of kids in the water, you immediately assume the worst: that they're about to be Jaws'd. In the video below, two orcas appear swimming near a pair of kids, scaring bystanders and the children alike.
Naturally, the sight of an animal, especially a large one, swimming towards you in the ocean makes for a rather alarming visual. And orcas unfortunately hold a reputation for being aggressive with humans.
True, in captivity an orca may attack its trainer, but orca attacks in the wild rarely ever occur. Typically, when it comes to humans, orcas tend to be "killers" in name only.
Still, the tension in the video is palpable until the moment the orcas swim past the kids. In the end, no one really needed to worry about anything, but in the large and unknown ocean, fear is a natural response.