Veteran US swimmer Diana Nyad successfully completed Monday a marathon crossing from Cuba to Florida, becoming the first person to do so without a protective shark cage.

The 64-year-old, who left a Havana yacht club early Saturday, arrived on a Key West beach to realize her lifetime quest on the fifth try, her team said in a tweet.

"Our #FearlessNyad has at long last achieved her #XtremeDream and reached #TheOtherShore," the tweet said. "An historic moment that proves #DreamsDoComeTrue"

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 homestretch.

Doctors -- monitoring Nyad from support boats shadowing her -- 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 had 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.

Australian Susan Maroney is the first and only person who has managed to swim across the Florida Straits. Protected by a shark cage, she did so in 1997 when she was 22.