"We have no confirmation on the species," said Cain. "But all four have the characteristics of a shark bite and not another marine animal bite."
Cain said pictures of the injuries have been sent to the University of Florida to try and find out what type of shark is responsible.
"We may never be a hundred percent sure what kind of shark it was," said Cain.
Tourist Karen Minton was the first to help one of the victims on Thursday. She was on the beach when an 18-year-old girl came out of the water screaming and with bites on her hand and feet.
"I asked her if she was sure it was a shark," said Minton. "She said 'yes, I tried to pry it off my foot with my hands and that's when it bit my hand'."
Minton said the girls injuries left a puddle of blood in the sand, and she believes the incidents are still on beachgoers' minds.
"There is a lot less people in the water than there was yesterday," she said.