Senior US distance swimmer Diana Nyad resumed her daring third attempt to cross the shark-infested sea from Cuba to Florida early Sunday, after receiving treatment for jellyfish stings.

The 62-year-old, who is seeking to become the first person to make the 160-kilometer (100-mile) swim without a shark cage, was weakened by a series of stings after starting her journey on Friday night.

"She’s back in! At 12:20am ET, Diana has re-entered the water. She is accompanied by three shark divers and the swim has resumed," her support team wrote early Sunday in a blog post on her site diananyad.com.

After suffering multiple jellyfish stings earlier in her swim, as well as breathing difficulties, Nyad was struck in the face and eyes late Saturday by what her team said was another "presumed jellyfish."

Nyad was removed from the water for treatment, but because she was not out of the water to rest, an independent observer from the International Swim Federation said the endurance swimmer could continue her bid for a record.

"Since Diana stopped to receive medical treatment, and continued at the EXACT spot where she stopped, the rules say she is now going for a record staged swim rather than a non-stop swim," her team said early Sunday.

Nyad -- who had completed roughly half the journey as of late Saturday -- is undertaking the record attempt with a range of equipment to try to keep her safe from sharks in these shark-infested straits.

On Saturday, a white shark was spotted near her but not too close for comfort, her entourage said on Twitter.

"Around 1pm -& don't everybody get excited here - an Oceanic white tipped shark was spotted near Diana in midst of the three boat flotilla," it said.

"Diana is deeply committed to safety of these extraordinary animals."

The veteran swimmer has been given prednisone, an anti-inflammatory drug, along with oxygen and other medication during her journey.

Nyad failed on two previous bids, in 1978 and again last month, in her quest to swim across the treacherous Florida Straits from Havana to Key West, Florida.

"You're doing better. I can see it," Bonnie Stoll, her chief handler, was quoted as saying on Nyad's blog.

Shoulder pain, asthma and ocean swells hobbled Nyad's August attempt.

She set out anew from Havana on Friday at 2204 GMT.

Nyad set an open sea record by swimming from the Bahamas to the Florida Keys -- a journey that is the same distance as the Cuba-Florida swim, but a feat she described as much less dangerous.

The swimmer set a record for circling the island of Manhattan at the age of 50, clocking in at seven hours and 57 minutes.

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