(NECN: Kathryn Sotnik, Chatham, Mass.) - "Cape Cod Shark Hunters" says they spotted a great white shark, estimated to be about 15 feet long, off the beach of Chatham, Mass. Sunday.
They say they followed the great white by air for about a mile off the coast line while it "stalked" seals.
The sighting, however, is not deterring many people from swimming at the nearby Lighthouse Beach in Chatham, including a family from Denmark. The beach is open to swimmers.
Christopher Spangenberg says, "We were just at the coastline so we didn't go too far out. We were only two to three meters in the water."
Others at the beach Monday took special interest in the shark sighting, and recent seal sightings, gazing though binoculars at the ocean.
"I've been coming down to Chatham for the past 15 to 20 years and I've never seen the seals come this close before to the swimmers," says Mary Adamcyk of Boston.
Marty Komertz of Ohio tells us he saw 500 to 600 seals out at one point.
Cynthia Wigren of the non-profit group, Atlantic White Shark Conservancy, helps raise funding for shark research and tagging off the Cape. She says the timing of this great white shark spotting is what "biologists thought it would be, very similar to the last three years."
Wigren says we may be seeing more sharks because there's definitely been an increase in the seal population. She says there's been exponential growth recently since seals have been protected under the marine mammal protection act."
Wigren advises against swimming too far out in the ocean, to not swim at dawn and dusk, not to swim near seals, and not to wear shiny items like silver jewelry that a shark may mistake for fish scales.
Last year beaches were shut down on the Cape because of numerous shark sightings.
A father of two was even bitten by a great white off the coast of Truro. He suffered severe leg injuries.
This year already Nauset beach was shut down for a short period of time in Orleans after a lifeguard spotted a dorsal fin about 150 yards off the beach.
Click here for more information on the Atlantic White Shark Conservancy.