Thousands of visitors are swarming to beaches in South Florida, but not the kind welcomed by the chamber of commerce: sharks. Their annual migration up the East Coast is taking place later than usual this year, coinciding with the start of spring break season, reports ABC News. Several beaches had to close earlier this week, reports the Palm Beach Post, though all were back open as of today. Researchers at Florida Atlantic University have counted 15,000 sharks so far, most within 200 yards of shore. The most common are blacktip and spinner sharks, about 4 to 5 feet long. But it’s not all gloom and doom: “The sharks are drawing attention for their natural showmanship, as well,” writes Patrik Jonsson at the Christian Science Monitor. “They’re often seen making spinning jumps out of the water.