City paramedics and emergency medical technicians treated more than 20 people, 10 of whom were sent to emergency rooms in serious or critical condition Tuesday, during the annual — and often chaotic — Independence Day “floatilla” off Waikiki Beach.

Hundreds of event participants had to be pulled to shore by lifeguards and other rescue workers, Honolulu Emergency Services Department spokeswoman Shayne Enright said. All of those taken to the hospital were treated for intoxication and/or injuries related to alcohol, and all were from 17 to 26 years old, she said.

A woman, 19, was in critical condition due to intoxication, she said.

The day started quietly, but from about 2 p.m. “one after another medical emergency came in,” Enright said.

Four city lifeguard jet ski crews, double the regular complement, were in action, and they stayed overtime until 7:30 p.m. bringing people ashore, Enright said.

They were joined by 14 Division of Conservation and Resources Enforcement officers assigned by the state Department of Land and Natural Resources, as well as two Coast Guard patrol boats, according to DLNR spokesman Dan Dennison.

With an estimated crowd of 8,000-10,000 between event attendees and regular beachgoers, “lifeguards say this was one of the most dangerous ‘floatillas,’ when it comes to the number of emergencies that were responded to,” Enright said.

There was a swarm of activity on the beach from about early afternoon as city lifeguards and state enforcement officers on jet skis brought more and more people back to shore. The Coast Guard picked up at least four people.

A man who appeared to be in his 20s needed his head bandaged by emergency services personnel at the lifeguard stand in front of the Waikiki police substation around 5 p.m.

Santa Rosa, Calif., resident Alex Coresey, 33, said that he and his wife, Cassie, were on the beach and saw up to 70 to 80 people brought ashore by rescuers on jet skis during a span of several hours. “Every couple minutes,” he said.

A lot of those being brought in appeared to be intoxicated, and some looked underage, he said.

The largely unorganized “floatilla” consisted of hundreds, if not thousands, of people in various motorized boats and inflatable water toys in relatively shallow waters about a half-mile offshore.

Due to brisk offshore wind, as the afternoon wore on, enforcement officers asked eventgoers to move closer to shore and to moderate alcohol consumption, Dennison said.

Juan Contreras, 22, of Portland, Ore., joined his friends in the ocean using a $4.50 plastic tube he purchased from an ABC store. In the water he saw turtles and picked up trash that he thought would be dangerous for the animals.

He said he never got to where the bulk of the party was taking place and did not drink any alcohol, but saw many go by him who did. If people were intoxicated, they probably had a hard time swimming back in due to sheer exhaustion, he said.

“I’m in decent shape but it was hard for me,” he said. “It’s not safe mixing alcohol with the ocean. The ocean is a dangerous place — a beautiful place but a dangerous place.”