Sept. 6, 2009 -- The weather might feel right for a taking a dip, but for those on the coast of Chatham, Mass., now's not a good time for one last summer swim.
Recent sightings of four great white sharks have prompted a swimming ban for the rest of the Labor Day weekend at some of the area's oceanside beaches, including North Beach, Lighthouse Beach, South Beach and Hardings Beach and Nauset Beach.
"While it is rare for a shark to strike and attack a human in the water, it can happen and given the recent local shark sightings, swimmers should exercise caution while swimming in Chatham's ocean waters," Chatham's harbormaster and parks and recreation director said in a statement Thursday, the day the sharks were first spotted. "In particular, people should avoid swimming in waters in the direct proximity of seals where sharks may be in search of prey."
According to ABC affiliate WCVB, the sharks came within 75 yards of the coastline.
Early Sunday, Gregory Skomal, a senior biologist with Massachusetts' Division of Marine Fisheries, and a team of Cape Cod fishermen successfully tagged two of the great white sharks, placing motion-tracking satellite tracking devices on them as they swam off the coast of Chatham.
While the ban on swimming is bad news for Labor Day vacationers, the locating and tagging of the great whites is a scientific boon.
Skomal and researchers like him use the tags to record where sharks travel with the goal of better understanding their migratory patterns. Great whites tagged off the coasts of South Africa and Australia offer researchers important information about how human activities, like fishing, affect sharks.
"From a scientific perspective, it's fantastic," Skomal told the Cape Cod Times Saturday, two days after the shark sightings were first reported. "We're pretty excited to be putting together the pieces of the puzzle."
Cape Cod Beaches Closed After Great White Sharks Spotted
Many shark species, including makos, blue sharks and thresher sharks, swim in and out of New England waters each year, according to Massachusetts' Division of Marine Fisheries.
The sharks are common in the area because of the thousands of seals that reside on the coast.
The Associated Press and ABC affiliate WCVB contributed to this report.