Some beaches remain closed in southeast Florida on Wednesday as hundreds of sharks (search) swarm offshore. Some have come within 20 feet of the shoreline.

The sharks have been repeatedly spotted near shore over the past two weeks in Broward (search) and Palm Beach (search) counties.

Experts said sharks congregate off South Florida every year in March and April to feast on sardines, herring, anchovies and other fish; before migrating.

One expert with the National Oceanic and Atmospheric Administration (search) says the big fish are preparing to migrate north. He says they'll travel as far as North Carolina, where the females will have "pups."

Although these sharks aren't considered "man-eaters," they have been known to bite swimmers.