LONDON -- Manny Huerta was never supposed to compete in the Olympics. It was a preposterous dream for a scrawny kid in Cuba who loved to swim in the ocean with the spear fishermen of Miramar Beach.

The Olympics? A fantasy for a poor immigrant in Miami who had no bike, nowhere to run.

But Huerta was one of 55 triathletes diving into brisk Serpentine Lake, cycling past Buckingham Palace and running around Hyde Park on Tuesday as 200,000 spectators lining the course shouted the name on his bib.

“Come on, Huerta!” they cried.

Most of them had no idea how far Huerta had come to get to London. From an inner-city high school. From a Little Havana junior triathlon team held together on a shoestring by his first mentor. From the backyard pool of a family that made him one of their own.

But Huerta’s mother knew all about the journey, because she had been with him, all the way to the starting line of the 2012 Olympics. She sacrificed her career so her son could have one as a triathlete.

It was all worth it as Martha Cardenas watched her son cycle under the Wellington Arch and run past the Princess Diana Fountain.

“It’s a dream I’ve been saving,” she said. “Now it has come to light.”

She could see Huerta was struggling. He emerged from the 1,500-meter swim near last place, scraped off his wetsuit, buckled on his U.S.A. helmet and slid onto his bike. He made up some time during the 25-mile bike portion, bridging from the last group to the middle pack. But not nearly enough to be anywhere close to Great Britain’s Brownlee brothers, Alistair and Jonny, or Spain’s Javier Gomez.

“Vamos, Manny!” Cardenas shouted when he passed, her hands clasped. Huerta’s girlfriend, Pierina Luncio, and friends from South Florida yelled and waved a sign. But they could tell he wasn’t right.

He started to feel queasy after the swim. On the bike he got cramps. And then he began vomiting.

“I threw up dinner and then breakfast and then anything else left in there,” Huerta said. “I threw up so much that the muscle contractions made it feel like someone punched me in the stomach.”

Yet on he went, slipping out of his bike shoes, dashing into the transition area, removing helmet, pulling on running shoes. In triathlon, a combination of three incompatible sports, there’s no time to pause, no time to let your aching thighs recover before asking them to run six five-minute miles.

“I didn’t want to give up,” Huerta said. “The crowd was amazing, my family and friends were in the stands and a lot of people in Miami were watching.”

People like Ralph Garcia, who had recruited 13-year-old Huerta to his Phantoms triathlon team, driving them to the Hadley Park pool, lending them donated bikes for races. Or the folks at Pinecrest Fitness and Ludus Tours, who raised money for his mother’s travel expenses. Or the Cubanos at Bikes To Go, the pals on the Hammerheads, the regulars at Jose Marti pool.

“Miami kind of adopted Manny,” said Gabby Pozo, who flew to London with husband Robert and daughter Nina to cheer for Huerta, whom Robert had coached in their pool, on runs through their Palmetto Bay neighborhood, on rides to Key Biscayne. Sometimes he spent weekends at their house. Robert, a race organizer, would waive Huerta’s registration fees in return for his help at the course.