Beautiful Monomy Island off the Cape’s elbow is home to an estimated 15,000 seals. Once near extinction, the seals live in in federally protected waters off the coast of Chatham. They are re-populating  in huge numbers and these "lions of the sea" have become feeding grounds for another majestic creature: the great white shark.

For their second August, a team of scientists on board a vessel called Ocearch have been trying to capture and tag the dorsal fins of great white sharks off the coast of Cape Cod. The tags tell them where the sharks go, and how far they travel.

It's a way for the scientists determine if the sharks are swimming too close to surfers or swimmers.

"Somebody was bitten last year off Truro, so the more data we have on the movement of these animals- where it is in the Cape Cod region as well as other parts of the U.S., the better equipped the beach managers will be in the Cape Cod area," said Greg Skomal, a program director for the Massachusetts Fisheries Department, onboard the research vessel.

Twelve long, hot hours a day the Ocearch research team churns out the chum and scans the waves for a single dorsal fin to pop out. Yet, so far they haven’t hooked a single great white on this trip.

"We've seen 10 sharks, so there's no shortage of sharks," said Chris Fischer, the expedition leader on board Ocearch. "These sharks are super finicky. This is the most difficult expedition we've had in terms of getting sharks interested in what we have for them. It's never as difficult as [New England]."

Last summer, the team managed to tag two females off the coast of Cape Cod, including a 16 footer they named Mary Lee.

Once caught, they covered the shark's head and a put a water hose into her mouth. Scientists have only 15 minutes to take an ultrasound, draw blood, and attach the tags that will relay information about their living habits such as when the sharks arrive in the Cape waters, when they leave, and where they spend most of their time.

Learning more about sharks is the primary focus of Ocearch, a non-profit organization that tracks the animals in waters all over the world and posts the info on their website.

Another top priority for the research team is protection of the animals, which are hunted and killed to make soup in other parts of the world

"200,00 sharks will be finned today and 200,000 tomorrow.  Are we really going to trade the future of the ocean for a bowl of soup?" asked Fischer.

The great white shark is a vital part of the Atlantic’s delicate eco-system. Without the sharks, seals could become overpopulated on Cape Cod.  And since seals eat fish, that would leave a depleted supply for commercial fishermen.

"It is the top of the food chain. It is the great balance keeper. And, if we lose the balance of the keeper of the ocean, we will lose the ocean," Fisher said.

Update: Ocearch researchers caught and tagged their first shark of the season on Aug. 15, after this piece aired.  Learn more about Ocearch here.