KEY WEST, FL - AUGUST 21: In this photo provided by the Florida Keys News Bureau, endurance swimmer Diana Nyad waves to her team after swimming a short distance from a support boat to shore August 21, 2012 in Key West, Florida. Nyad failed in a fourth attempt to complete a swim across the Florida Straits from Cuba to the Florida Keys. (Photo by Andy Newman/Florida Keys News Bureau via Getty Images)
Diana Nyad swam into the history books, completing a marathon three-day crossing from Cuba to Florida to become the first person to do so without a protective shark cage.
The 64-year-old American, who left a Havana yacht club early Saturday, arrived on a Key West beach on Monday to realize her lifetime quest after four previous attempts failed amid stormy weather and jellyfish attacks.
"I've got three messages," a visibly exhausted Nyad, her face puffy and sunburned, told cheering crowds as she walked ashore.
"One is, we should never, ever give up. Two is, you never are too old to chase your dreams."
"Three is, it looks like a solitary sport, but it's a team," Nyad added in a nod to her supporters. She was accompanied by five boats and a team of divers as she braved the perilous waters.
Initially, the veteran swimmer had hoped to complete the treacherous 100-mile (160-kilometer) trek in 80 hours. But in the end, she did it in 52 hours, 54 minutes and 18.6 seconds, according to her Facebook page.
"Diana Nyad, 64, has successfully and powerfully realized her #XtremeDream," the posting said.
"Her eyes burned with intensity, her body refusing to quit."
Nyad's pursuit was followed closely by people around the globe, who took to social media to first encourage and then congratulate her.
Even the White House, preoccupied with the conflict in Syria, tweeted on behalf of President Barack Obama: "Congratulations to @diananyad. Never give up on your dreams."
Former Secretary of State Hillary Clinton also saluted Nyad.
"Flying to 112 countries is a lot until you consider swimming between 2. Feels like I swim with sharks -- but you actually did it! Congrats!" she tweeted.
Live television footage showed crowds swarming the beach and even wading toward Nyad as she approached the shore.
But challenges loomed large during the historic crossing -- especially on the home stretch.
Doctors monitoring Nyad from the support boats reported early Monday that her tongue and lips were so swollen that her speech had become slurred.
She also experienced extreme cold overnight, they said.
As Nyad approached Key West, large jellyfish appeared in her path. To keep her from suffering a debilitating sting, divers swam ahead of Nyad looking for more.
In a display of endurance and spirit, Nyad actually increased her average speed to 1.76 miles per hour Sunday after more than 24 hours in the water.
When necessary, Nyad wore a full-body suit. She also had a specially designed prosthetic face mask as well as gloves and shoes at her disposal to protect herself from jellyfish stings.
A year ago, Nyad ended her fourth bid to cross the stretch after battling lightning storms and blooms of jellyfish for more than two days.
In media interviews she said she could handle the sharks and the bad weather, but wondered aloud whether the swarming, stinging jellyfish had made the feat simply impossible.
Australian endurance star Chloe McCardel, 28, scrapped a similar bid to swim non-stop from Cuba to Florida earlier this year after a debilitating jellyfish sting.
Nyad's first attempt was in 1978, when she was 28.
Nyad set an open sea record for both men and women by swimming from the Bahamas to the Florida Keys in 1979 -- a journey that is about the same distance as the Cuba-Florida swim, but which she has described as far less dangerous.
At a news conference on Friday, the veteran expressed confidence that she would persevere this time around.
She said her dream of 35 years also sought to bring communist Cuba and the United States -- which have been at odds for decades -- closer together.
Australian Susan Maroney was the first person to swim across the Florida Straits, in 1997, when she was 22. But she was protected by a shark cage, which gives an added boost to a swimmer.