Sharks are generally seen as the terrors of the ocean (a title that was unfairly cast upon them as a result of the popular 1975 film “Jaws”). Really though, you shouldn’t worry about shark attacks (no matter how numerous they may be). Really, not at all. According to the International Shark Attack File (ISAF), which is funded by the Florida Museum of Natural History at the University of Florida, between 1580 and 2013 there were a mere 2,667 confirmed unprovoked shark attacks around the world. That may seem like a high number, but some two thousand attacks over 433 years adds up to just over 6 attacks a year. And with over 7 billion people on the planet, those numbers are hardly alarming.
Moreover, ff these attacks, only 495 were fatal. Now, I don’t want to diminish nearly 500 deaths, but again, over the course of some 433 years, it is nothing to cause alarm. In fact, many, many more people drown in the ocean every year than are bitten by sharks. According to the CDC, in 2004 alone, there were 3,308 unintentional drownings in just the United States. So ultimately, one could consider the mere act of swimming in the ocean more dangerous that a shark attack.
So if you ever see something forming like the hoard (the real term is "shiver") that you see in the video below, don't worry too much. This is what happens when a fishing boat comes across an area with sharks and they start throwing out the catch they don't want.