Adalberto Roque / AFP - Getty Images

Australian swimmer Chloe McCardel jumps feet-first from Marina Hemingway in Havana, on June 12. McCardel is attempting to become the first to cross the Florida Straits swimming through the shark-infested sea without a protective cage.

Updated on June 6 at 10:30am ET: After swimming for 11 hours, McCardel abandoned her attempt due to a "severe debilitating jelly fish sting," according to a statement from her support team.

Australian endurance swimmer Chloe McCardel jumped feet-first into the water off of Cuba Wednesday in an attempt to become the first person to swim from Havana to Florida without a protective shark cage. 

Arriving at Havana’s Hemingway Marina in a pink 1950s Chevy convertible, McCardel thanked her Cuban hosts, promising she’d be back again. Her husband helped lather grease around the edges of her one-piece bathing suit to prevent chafing as she put on her swim cap and goggles.

Desmond Boylan / Reuters

Australian long-distance swimmer Chloe McCardel starts her attempt to swim to Florida from Havana June 12. With favorable weather predicted and a team of scientists on her side, McCardel will set out on Wednesday to become the first person to make the 103-mile (166-km) swim between Cuba and the Florida Keys without a shark cage to protect her. The treacherous body of water known as the Florida Straits is the Holy Grail for marathon swimmers and has been conquered only once, by Susie Maroney, also Australian, who used a protective cage at age 22 during her 1997 swim that glided on ocean currents and enabled her to make the journey in just 25 hours.

The approximately 100 mile swim through shark and jellyfish infested waters from Havana to the Florida Keys is expected to take about 60 hours.

Roberto Leon / NBC News

Australian endurance athlete Chloe McCardel strokes through the balmy waters off Cuba in an attempt to become the first person to swim from Havana to Florida without a protective shark cage. She is accompanied by kayakers and a support boat.

McCardel is not the first to attempt the crossing without a cage; two other swimmers have made four failed attempts since 2011.

“More than 20 people across history have tried to swim across this amazing stretch of water, the entire Gulf Stream, with the sharks, the jelly fish over such a long distance, 103 miles, about 166 kilometers and it is the hardest swim in the world today,” McCardel said during a press conference in Havana Tuesday.

She laid out the perimeters of the challenge: “I will not wear a wet suit. I will not use a shark cage. I will not hold on to anything. I will not get on the boat at any time.”

Adalberto Roque / AFP - Getty Images

Australian swimmer Chloe McCardel gives her thumbs up before departing from Marina Hemingway in Havana, on June 12. McCardel will attempt to become the first to cross the Florida Straits swimming through the shark-infested sea without a protective cage.

McCardel has an extensive team of scientists who will be helping her navigate the finicky Gulf Stream from land – feeding information to her support boat. She will also be deploying a piece of equipment called a Shark Shield to create an electromagnetic field around her meant to discourage the predators from getting too close, according to the Associated Press.

With a graceful freestyle stroke she set out accompanied by two kayakers and her support boat. 

NBC News' Roberto Leon and the Associated Press contributed to this report.

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All photos by Joe Raedle / Getty Images

Top: Guy Davies shows a dead insect he found in an orange grove on May 13, in Fort Pierce, Fla. Bottom: Tangerines are seen in a bin as the citrus industry tries to find a cure for the disease "citrus greening" in Fort Pierce, Fla.

Guy Davies, an inspector with the Florida Division of Plant Industry, checks an orange tree for the insect Asian citrus psyllid that carries the bacterium causing disease, "citrus greening" or huanglongbing, from tree to tree on May 13, in Fort Pierce, Fla.  Davis is part of a team trying to track the movement of the insect. There is no known cure for the disease that forms when the insect deposits the bacterium on citrus trees causing the leaves on the tree to turn yellow, the roots to decay, and bitter fruits to fall off the dying branches prematurely. Steps continue to be taken to try and combat the disease, but none have stopped the attack on the citrus business as it spreads from Florida to other citrus producing states.

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Guy Davies uses a stick to hit the leaves on a grapefruit tree hoping to dislodge into the container the insect Asian citrus psyllid on May 13.

Jeff Langlois / The Palm Beach Post via ZUMAPRESS.com

A pod of spinner sharks is seen through a wave at Midtown Beach on Thursday.

Several beaches along South Florida's Atlantic coast line were closed after thousands of sharks were seen migrating in the waters.

The sharks were migrating from Boca Raton to Jupiter since the beginning of March, marine biologists told NBC Miami.

Read the full story.

Brian Blanco / Reuters

Supporters hold a candlelight vigil at the exact moment when teenager Trayvon Martin was shot one year ago by neighborhood watch volunteer George Zimmerman in Sanford, Florida Feb. 26, 2013. The fatal encounter between Martin and Zimmerman has thrown the spotlight on gun control and Florida's much criticized "Stand Your Ground" statute, also known as a "shoot first" law, which was signed into law by former Governor Jeb Bush in 2005. The attendees symbolically wore hooded sweatshirts as Martin was wearing one at the time of his death. Read the full story.

Matthew Stockman / Getty Images

Brad Keselowski, driver of the #22 Discount Tire Dodge, and Kyle Larson, driver of the #32 Clorox Chevrolet, are involved in an incident at the finish of the NASCAR Nationwide Series DRIVE4COPD 300 at Daytona International Speedway on Feb. 23, in Daytona Beach, Fla.

Regan Smith was leading coming to the checkered flag when he was turned sideways into the wall. Cars began wrecking all over the track, and rookie Kyle Larson's car went sailing into the fence that separates the track from the grandstands.
 

Stewart slid through the wreckage to the win.

-- By Jenna Fryer, The Associated Press

Read the full story. 

Chris Graythen / Getty Images

Matthew Stockman / Getty Images

Matthew Stockman / Getty Images

Kyle Larson, driver of the #32 Clorox Chevrolet, looks at his car following the crash.

Matthew Stockman / Getty Images

Medical personnel assist fans sitting close to the wall following the crash.

Brian Blanco / Reuters

Jim Foster, leader of the North Florida Survival Group, radios group members to check their status as they perform a land navigation drill.

Brian Blanco / Reuters

A member of the North Florida Survival Group puts a mask on his son as they gear up to perform enemy contact drills in a wooded area during a field training exercise in Old Town, Florida.

Reuters -- The North Florida Survival Group group trains children and adults to handle weapons and survive in the wild. The group passionately supports the right of U.S. citizens to bear arms and its website states that it aims to teach "patriots to survive in order to protect and defend our Constitution against all enemy threats." Photographer Brian Blanco writes about his experience:

Jim Foster is a 57-year-old former police officer and the leader of the North Florida Survival Group. Jim was the man who, after feeling out my intentions in a two-hour meeting at a chain restaurant a few weeks earlier, had granted me permission to photograph his group’s field training exercise. It was an opportunity I snatched up without hesitation. It’s not every day that a photojournalist gets an invitation to shoot a militia gathering. Understandably, they tend to be fairly secretive groups who don’t exactly keep the media on their Christmas card lists.

Foremost on their minds was gun confiscations. Meeting the group just a few weeks after the re-election of Barack Obama, the prevailing concern among the group was when the next gun ban would be coming and how they should stockpile ammunition and weapons to prepare for it.

Read more on the Reuters Photographers Blog.

Editor's note: Pictures taken on Dec. 8, 2012 and made available to NBC News today.

Brian Blanco / Reuters

Brianna, 9, of the North Florida Survival Group hands an AK-47 rifle to Jim Foster, 57, the group's leader, before heading out to conduct enemy contact drills.

Brian Blanco / Reuters

A young boy sits on a toy, upset because his sister got to carry the rifle that he wanted.

Brian Blanco / Reuters

Jim Foster (center) critiques the performance of group members during an enemy contact drill.

Related on PhotoBlog:

• 'Teeth of the Constitution:' Light Foot Militia rises in Idaho's backcountry
• Missile launcher appears at Seattle gun buyback event
• White House releases photo of Obama firing gun

Joe Skipper / Reuters

U.S. Senator Bill Nelson, left, walks with Florida Wildlife Commissioner Ron Bergeron as they take part in a hunt for pythons during a state-sponsored snake hunt in the Everglades, Fla. on Jan. 17. Python Challenge 2013 is a month-long event sponsored by the Florida Fish and Wildlife Conservation Commission offering prizes of $1,500 for the most pythons captured and $1,000 for the longest python.

By Barbara Liston, Reuters

A python hunting competition starting on Saturday is drawing hundreds of amateurs armed with clubs, machetes and guns to the Florida Everglades, where captured Burmese pythons have exceeded the length of minivans and weighed as much as grown men.

"I just thought it was as exciting as could be. It's a once- in-a-lifetime opportunity," said contestant Ron Polster, a retired salesman from Ohio whose closest encounter with the swamp has been from the highway heading south for the winter.

The stated goal of the competition is to raise awareness of the threat Burmese pythons pose to the Everglades ecosystem. The snakes are native to Southeast Asia and have no known predators in Florida. Full story

Joe Skipper / Reuters

A previously captured 13-foot Burmese python is held by Capt. Shawn Meiman for the press to view before U.S. Senator Bill Nelson took part in the state-sponsored snake hunt.

Joe Skipper / Reuters

An airboat with U.S. Senator Bill Nelson aboard skims across sawgrass during a hunt for Burmese pythons during the state-sponsored snake hunt, in the Everglades, Fla. on Jan. 17.

Joe Skipper / Reuters

A previously captured 13-foot Burmese python is held for the press to view on Jan. 17.

Brian Blanco / Reuters

Gun shop customers shop for weapons as they listen to a live stream of a President Barack Obama's gun control proposals at the Bullet Hole gun shop in Sarasota, Fla. on Jan. 16.

President Barack Obama proposed a new assault weapons ban and mandatory background checks for all gun buyers on Wednesday in a bid to channel national outrage over the Newtown, Conn. school massacre into a new push for gun control.

"While there is no law or set of laws that can prevent every senseless act of violence completely, no piece of legislation that will prevent every tragedy, every act of evil," Obama said at a mid-day announcement at the White House, "if there's even one thing we can do to reduce this violence, if there's even one life that can be saved, then we've got an obligation to try it." -- Read complete article.

The National Rifle Association, the country's most powerful gun lobby, released a statement Wednesday afternoon in response to the president's remarks.

"We look forward to working with Congress on a bi-partisan basis to find real solutions to protecting America's most valuable asset - our children. Attacking firearms and ignoring children is not a solution to the crisis we face as a nation," the NRA wrote. "Only honest, law-abiding gun owners will be affected and our children will remain vulnerable to the inevitability of more tragedy."

Related Links:

• Obama unveils sweeping new gun control proposals
  
• Obama's gun plans spark little enthusiasm with key lawmakers
• Stop gun violence, kids ask President Obama in handwritten letters

Slideshow: As it happens: Obama's fourth year in office

Robin Buckson / AP

The president's fourth year at the White House in pictures — follow along as it happens.

Launch slideshow

Mahesh Kumar A / AP

A shopkeeper shows a wall clock to a customer at 12 hours 12 minutes on 12-12-12 at a shop in Hyderabad, India, Dec. 12, 2012.

Joe Raedle / Getty Images

People participate in a 12-12-12 ceremony with crystal skulls at Miami Circle, formerly a Tequesta Indian site, in Miami, Fla., Dec. 12, 2012.

Ulet Ifansasti / Getty Images

Brides and grooms exchange rings during a mass wedding ceremony in Yogyakarta, Indonesia, Dec. 12. Twelve couples participated in the mass wedding globe to mark the once in a century date of 12-12-12.

Rajesh Kumar Singh / AP

A pediatrician checks babies born on 12-12-12 at a hospital in Allahabad, India, Dec. 12. The day, seen as auspicious by astrologers, saw an influx of mothers to hospitals looking to give birth that day, local media reported.

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