They lurk below the waters just a stone's throw from the beaches off Cape Cod and the number spotted in recent years has grown. White Sharks -- popularly referred to as "great whites" -- are seeking seals for dinner and the exploding population is drawing the predators close to shore.
This summer alone, dozens have been spotted.
It's a nerve-wracking situation for authorities who aim to keep beach-goers safe but it also offers a unique opportunity for researchers who've taken on an adrenaline pumping initiative to tag the massive hunters, study their movements and eating habits.
Gregory Skomal, a fisheries scientist with the Massachusetts Division of Marine Fisheries, has spent decades studying fish in the Northeastern waters, including sharks.
"Blues, threshers, makos, basking sharks, tigers you name it. I never thought we'd be working on White Sharks," said Skomal.
In recent years these massive hunters, some reaching over 20 feet long, have forced authorities to close beaches and warn swimmers to beware.
Skomal and his team use a modified harpoon method to tag the beasts which sometimes swim into shallow waters just ten feet deep seeking their dinner.
"It's our first real opportunity to study White Sharks here in the Atlantic Ocean and the only reason that's possible is because we've got a growing population of grey seals," said Skomal.
"That population of grey seals has reached a level that it's drawing these sharks close to shore."
Some of the tags are equipped with acoustic transmitters, alerting authorities to the sharks' proximity to shore. Others are sophisticated satellite tags offering a greater range of data, tracking the sharks for months over thousands of miles.
"As the picture emerges, as we tag more and more, we'll get a more comprehensive sense of how to conserve these animals, if it's necessary, and also give the beach managers a better picture, a more comprehensive picture of how to manage these beaches in terms of public safety," said Skomal.
The sharks arrive when the waters gets warmer, following their food source, and will stick around well into Autumn, some remaining in the area into early November.
Molly Line joined Fox News Channel as a Boston-based correspondent in January 2006.