The sharks were spotted swimming within 50 yards of the beach, which drew a crowd to the coast.
Long Beach Lifeguards said 24-hour advisory notifications were posted along the beach, but the beach would remain open.
A shark advisory is issued when "there is a confirmed sighting of a non-aggressive shark."
"They have not acted in any sort of threatening behavior. The water is not closed, the beach is not closed. We just want people to know that they're out there," said Capt. Cameron Abel, with the Long Beach Fire Department's Marine Safety Division.
A crew in a tow boat got an up close look at the sharks cruising in the waters. Officials said most were around 6 feet long. Beachgoers were thrilled to catch a glimpse.
"I've seen the fin when the shark comes out. You could see the actual fin, one of the fins that come out. But then they go back in because they don't really want to see people or big movement," said Christian Rivera, of Signal Hill.
ABC7 meteorologist Leslie Lopez was in the area and caught one of the sharks showing off its fin on camera.
The sightings stretched from Long Beach out to southern Orange County.
The Orange County sheriff's helicopter spotted about 15 sharks in the water.
Some who gathered along the shore waded out into the water because they wanted to see the great whites in person.
Officials said the ecosystem is so healthy, which brings an abundance of food, such as sting rays and halibut, to the coast for the sharks to eat.
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