Miami-Dade Fire Chief David Downey said 24 people were taken to area hospitals. Two people were in serious condition.
Authorities said about 100 people were on the deck of Shucker's Bar & Grill in North Bay Village, north of Miami Beach, when it gave way.
Sports bar customers — and later rescuers — helped people from the water amid yelling, crying and a rush to find people who might be submerged.
"According to witnesses, a lot of people jumped in to help," Downey said.
One witness, Martin Torres, 42, of Los Angeles, said he was inside the sports bar with family and friends when heard a loud explosion. At first, he thought a boat had struck the deck. He said he looked outside and saw people staring up from the water, and then he and others started helping them out of the bay.
"It was shock," said Torres. "People were yelling. Nobody knew. People came out all wet. They were crying. For a while, nobody knows what was going on."
Marquez said he looked out at the deck and "it all came down in slow motion."
Many peoples seemed in shock, with cuts and gashes on their faces. He said he went to the edge and helped five or six people from the water, and then a swarm of rescuers arrived.
"A lot of people were just shaken up," added Eric Williams, 42, of Atlanta. He rushed to the scene with his son and they jumped in to help people after they heard a loud noise from their room at the adjacent Best Western.
But he described the scene as "pandemonium," with people scrambling to get out.
There was initially some concern that people might have been trapped in the water beneath the crumpled deck. But divers searched the waters as helicopters overhead shined spotlights onto the scene, and Downey said later that crews had completed their search and everyone was accounted for.
The accident occurred around 9:45 p.m. as customers were watching the Miami Heat play the San Antonio Spurs. The Heat won on the road.
WSVN-TV news director Tom Tuckwell said he had his back to the bay when he heard an enormous roar, according to the station's website. When he turned around, he saw people disappearing beneath them.
"That was a big gathering watching the Miami Heat and Spurs," said Miami-Dade Fire Rescue spokeswoman Griselle Marino. "There were a lot of TVs and everybody was in celebration and it was loud. So when it started happening, some people didn't even realize what was going on."
Torres said he looked down and "these girls were looking up. We started grabbing them. They got crazy. People started pushing toward us."
Lt. Eugene Germain, spokesman for Miami-Dade Fire Rescue, said most of those injured had cuts but one patient suffered a fracture.
He said 50 units responded, and divers were deployed — the water was about 4 feet deep right where the deck was — as air rescue units lit up the scene. Rescuers talked with eyewitnesses and they were able to account for persons they were with.
"We did an extensive search and after completing the search, we didn't find any other victims," he said.
Said Marino: "We could have had a lot more seriously injured people but right now it seems to be a very positive outcome."
Heat player Dwyane Wade said after the game that his thoughts were with the injured fans.
"I'd like to share our concerns as an organization and our gratitude to our fans back in Miami, but share our concerns for all that were injured tonight at Shucker's restaurant," he said.
North Bay Village is a small island in Biscayne Bay with a strip of restaurants, hotels, houses and condos that is attached by causeways to the mainland and also to Miami Beach. Pouring rain fell early Sunday near the Shuckers site, where a reporter later observed pilings sticking out of the water where the deck once was. Wood, chairs and palm trees were piled together in the water in a scene like after a hurricane.
Though not as trendy as South Beach, North Bay Village is one of the many tourist spots in and around Miami where locals and visitors converge.
North Bay Village Mayor Connie Leon Kreps went to the scene afterward and said she was grateful that no one had died.
"This is a real tragedy," she said. "Shuckers has been here for many, many years. People come from all around to enjoy the view and the food. This is really unfortunate."
She said the city would undertake a thorough investigation of what caused the collapse.