By Syma Chowdhry, Todd Quinones

LEWES, Del., (CBS) — What was supposed to be a fun, peaceful day at the beach turned terrifying for one teen.

Andrew Vance was swimming at Cape Hanlopen Beach on the Delaware Bay Monday evening.

Officials say it is unheard of for a shark to bite swimmers in this area.

“In 20 years I haven’t dealt with any shark bites, in state park history here,” Wayne Kline of State Park Police said.

By looking at the injury, experts believe he was bit by a young sandbar shark.

“Based upon the bite, this shark was not interested in feeding. It looked like it was an instinct bite,” shark biologist Scott Newlin said.

Marine biologists say it is common to see sandbar sharks this time of year in the Delaware Bay, but another factor could’ve drawn in more sharks.

“There was a large sturgeon carcass that has been on this beach for the past couple of days so it probably brought in a lot sharks in the area to feed on it,” Newlin said.

The 16-year-old was in about five feet of water when the shark bit his arm.

“The sharks in this area are placid and usually very rarely interacts,” Newlin said.

Experts also say this is the season that female sharks are giving birth.

“The females usually come into the bays and the estuaries up here to give birth to young, and then those young are still trying to figure out what they all need to do,” Kevin Becker of Adventure Aquarium said.

Despite that, beach-goers are a little apprehensive.

“I’m not going to into that deep if I know someone else just got bit. Plus the dolphins are swimming in pretty close too so it makes you wonder what else is swimming in kinda close,” beach-goer Michelle Becker said.

The beach was off limits to swimmers after the incident.

But it was reopened by Tuesday afternoon after State Park officials didn’t find any shark activity.

Experts stress this is uncommon, not something you’d see in a popular movie.

“No you won’t need a bigger boat, not this time,” Newlin said.

Vance needed 22 stitches. He is home now and is expected to be ok.