Heroic Brother Saves Surfer Struck By Lightning

A man thought his brother was "just gone" after being hit by lightning, but credited 'Bondi Rescue' for helping to save his life.

A man was struck by a lightning bolt while getting out of the water at Sydney's Dee Why beach on Monday afternoon, one of two people struck by lightning within 10 minutes in the city.

His brother, Lionel, was with him at the time the huge bolt hit.

"I looked around, like is everyone OK, then I saw my brother lying in the water," he told 10 News First exclusively.

"I sprinted over as fast as I could and he was just gone. Eyes completely open, just gone."

Responders work to revive Lionel's brother on the beach. Image: 10 News First

Lionel began giving his brother CPR, helped by other beachgoers, until an ambulance arrived just minutes later.

"I'd just seen 'Bondi Rescue' so I just jumped on him and started pumping his chest as hard as I could," he said.

His brother was taken to Royal North Shore Hospital in a serious condition.

"I just want to say thanks to the lifeguards, all the people on the beach, they were incredible," Lionel said.

"You know who you are, you helped save my brother's life."

Lionel has praised passersby who helped save his brother. Image: 10 News First

Just 10 minutes before the brothers' terrifying encounter, a woman in her 70s in Arcadia was struck in the chest by a lightning bolt.

She was treated by passers-by and paramedics before heading to Westmead Hospital in a critical condition. She remains in hospital.

NSW Ambulance Inspector Carolyn Parish said the circumstances were "extraordinary" and credited the first responders.

"This is the first time I have ever come across two lightning strikes within 10 minutes - it's terrifying," she said in a statement.

With AAP.