There were nine reported shark sightings on Cape Cod beaches yesterday, with the most harrowing by far occurring at Nauset beach, which stretches between the towns of Orleans and Chatham. Around 1:30 p.m., beachgoers spotted a dorsal fin in the water, followed by what one witness described as "blood everywhere." Fortunately, it was the blood of an unfortunate seal, not a human, but the source of all that blood was not immediately clear. Here's video of the panicked scene:

"I’ve never seen so much blood in my life," witness Pat O’Brien told the Boston Globe. "The seal was making a lot of noise, like it was screaming... It looked like the seal was trying to get on the shore, but there were so many people it was afraid."

As alarmed beachgoers scrambled to safety, several surfers from Brooklyn paddled frantically to shore. O'Brien and another person reportedly helped pull them to safety. "I heard yelling and screeching and thought the world was over," 16-year-old Samuel Scholonger of Brooklyn told the Globe.

"I just swam for my life right there, just dreading the moment the shark was gonna pull me in and suck me in," Zevi Greenspan of Crown Heights told NBC New York. And in an interview with NESN, Greenspan recalled, "I look on the left and I see my friend Nisi paddling for his life and I see something flubbering in the water with blood all around it. I thought it was a person."

The beach was closed to swimmers indefinitely shortly after 1:30 p.m., CBS Boston reports. The seal died. The humans survived.

Great white sharks were rarely spotted at Cape Cod beaches until the summer of 2009, when an increase in the grey seal population began attracting more of them, according to National Geographic. "The numbers we're seeing on a relative scale are increasing, in 2014 we counted 80 individuals over the course of the summer and just last summer that went up to about 147," Senior Fisheries Biologist Dr. Greg Skomal told ABC News at the end of June. "So there is a general increasing trend as more and more sharks recruit to the area."

Numerous sharks have been tagged and spotted by researchers off the coast of Cape Cod this summer, including an 11-foot shark dubbed "Hunter" that was first tagged off South Carolina and subsequently spotted near... Long Island.

You know what else besides the beach is fun in the summertime? Swimming pools!

Love, Mom.