The aquarium visitors, including four children, fell into a shark tank and thrashed around in terror for up to 15 minutes with the animals swimming beneath their kicking feet before they were pulled out.
No one was seriously hurt, though one of the children, a 2-year-old girl, later woke up screaming in the night.
Aquarium staff quickly helped the visitors out of the water after the incident on Wednesday night. The ruckus apparently scared the sharks, which are about 8 feet to 10 feet long, away from the frightened swimmers.
One of the onlookers, 8-year-old Amanda Kruse, said most of the sharks scattered, but she saw one cruising underneath the panicked guests.
"Its lips were peeled back and its teeth were showing," Amanda said.
"They weren't in any danger of being bitten by sharks," said Aquarium of the Americas spokeswoman Melissa Lee said Thursday. "The second it happened, those sharks took off."
The sharks are well-fed and are accustomed to people being in their 400,000 gallon tank, because divers are frequently in there, she said.
Officials at the Aquarium of the Americas were investigating what caused the accident at the Gulf of Mexico exhibit, which includes about 24 nurse sharks and sand tiger sharks. The aquarium Web site warns visitors: "You'll be glad you're on the outside looking in."
The catwalk is normally reserved for staff but was opened for a behind-the-scenes tour for aquarium members. When it buckled, the group was thrown into the 20-foot-deep, 400,000-gallon tank.
"All of sudden I heard something go bam, and the long catwalk split in half right in the middle and it dropped everybody straight into the water," said Dan Rooney, whose two daughters, 2-year-old granddaughter and 5-year-old nephew plunged in.
The water level is about 3 feet below the slick edges of the glass-walled tank, so there was no way for those inside to pull themselves out without help. Many clung to the mock oil platform in the center of the tank. Adults tried to hold small children above the water, splashing around and scattering sandals, makeup kits and brochures inside the tank.
"The water is clear so you could see the sting rays and sharks swimming beneath them," Rooney said. "I know the sharks are well-fed, but with all that splashing you wonder if their hunter instincts are going to kick in."
Like many of those who fell in, Erin Rooney, 14, was scraped by the barnacle-encrusted support poles of the mock oil platform.
"It happened so fast I didn't really think about the sharks at first, I just wanted to get out of the water," she said. "I never wanted to go near the sharks, and the worst part is I was scared to go on the catwalk and people were making fun of me for not wanting to go on it."
Erin's sister, Allison Rooney, 21, was able to hand 2-year-old daughter Amber to a rescuer after they fell in. But she had to swim to the other side of the tank to get out — and her rescue took 15 minutes.
"It was very scary," she told CNN. "When I first looked down, I saw a sting ray right underneath me and I just freaked out. I was scared to death what I would do if I saw a shark."
Allison Rooney said Amber was quiet during the accident.
"But on the way home, she started talking," she said. "Last night, she woke up quite a few times screaming, `Mommy, hold me!"'
Many of those in the tank got out on a makeshift bridge that aquarium workers stretched across to the oil platform.
Officials said the guests were in little if any danger.
"We didn't have `Jaws' in the aquarium or anything like that," said Ron Forman, president of the Audubon Institute, which runs the aquarium.
Dan Rooney said he pulled three people out before an employee told him to move away from the tank, but no immediate help came for Allison. He called for her to swim over to him and he pulled her out.
"If a shark had gone anywhere near I was ready to jump in — not that it would have helped — but I wasn't just going to stand there if my family was in trouble," he said
The aquarium was opened for business as usual Thursday.