Thousands of sharks, heading north after migrating to the south for winter, prompted beach closures along South Florida's Atlantic coastline. NBC's Brian Williams reports.

Several beaches along South Florida's Atlantic coast line were closed after thousands of sharks were seen migrating in the waters.

The sharks were migrating from Boca Raton to Jupiter since the beginning of March, marine biologists told NBC Miami.

Biologists said the sharks are going north after migrating to the south for the winter.

Lifeguards at Midtown Beach saw spinner sharks in the waters and put up red flags to tell beachgoers they couldn't enter the water.

"It's dangerous. It's not what you would expect. Families come out here to enjoy the weather, beach, and sand, but now they can't.They have to travel a little bit further than they should," said beachgoer Guirlene Exantus.

Doctors at St. Mary's Medical Center in West Palm Beach told WPTV that they see about five to six shark bite victims annually. These bites are usually minor, but can put the victim at risk for infections.

Swimmers are advised to swim close at beaches with lifeguards and take jewelry off before getting in the water as experts say sharks are attracted to silver, yellow and gold.

Jeff Langlois / The Palm Beach Post via ZUMAPRESS.com

A pod of spinner sharks is seen through a wave at Midtown Beach, Fla. A huge swarm of sharks has shut down beaches of Florida as they migrate up the East Coast.

Continue reading here:

Sharks swarm at Fla. beaches