Niamh, from Galway, and her friends had gone for a swim on Coogee beach when they heard the shark alarm.
The 25-year-old had just come out of the water when, the swimmer, identified as British ex-pat Simon Nellist, was killed by the great white in the first fatal unprovoked shark attack in Sydney since 1963.
“We went to use the bathrooms before sitting on the beach, Maeve was telling me this is the area they film Bondi Rescue on and told me they put flags up and sound alarms when there’s a shark in the water,” Niamh recalled.
She had only said it and this massive alarm came on so loud all over the beach, it was mad.
“I turned to her and said, ‘is that the shark alarm?’ and she wasn’t sure and neither were the rest of our friends,” she said.
She revealed how lifeguards told people on the beach and in the water to “get out for your own safety”.
“The incident was way up from where we were, but apparently it’s frequent for the shark alarm to be raised,” Niamh added.
“Considering there has been no fatal shark attack in Sydney for almost 60 years, I think people did not think it was so serious straightaway.
“The whole thing was a bit mad — they sent out jet skis from surrounding beaches to help with the search for the body.
“I was cautious about going into the water in the first place not even about sharks but whatever else is in there. I was in the water earlier that afternoon with Clair, I would definitely be so cautious about going back in again.”
According to the Examiner, the women were not aware someone had been fatally injured until they arrived back at their home.
“We were all shocked when we heard the news, we have no internet data so when we reached the house, one of the girls got a call from a family member asking us if we had heard about the Sydney shark attack.
“When we realised it happened close to where we were, we were shocked, it’s a bit surreal. My thoughts are with the swimmer who was attacked and their family, it is a truly tragic incident.”
Expat Simon Nellist was killed by the great white just 150m away from the beach at Buchan Point, near Little Bay in an "incredibly rare" attack.
He had been training for a charity ocean swim when he was mauled by the 15ft predator on Wednesday afternoon.
His remains were found in the water following the horror ordeal that happened at just after 4.30pm local time.
Simon, who is said to be an experienced ocean swimmer and diver, is thought to have family in the UK and was also reportedly due to marry his girlfriend in Sydney.
Witnesses said they heard the victim yell out for help in desperation as the shark "attacked vertically" before dragging the man's body out of the ocean.
Fisherman Kris Linto told Australia’s Nine News: "Some guy was swimming and a shark came and attacked him vertically.
"We heard a yell and turned around it looked like a car had landed in the water, a big splash then the shark was chomping at the body and there was blood everywhere.
"It was really bad."
One man described how he was fishing and saw a man wearing a wetsuit swimming across the bay.
He said the swimmer was right in front of him when he was dragged under the water by the shark.
The man told ABC: "He was yelling at first, and then when he went down there were so many splashes.
The shaken man said the attack lasted for several seconds.
He said: "It was terrible. I am shaking. I keep vomiting. It's very, very upsetting.
"He just went down for a swim, enjoying the day, but that shark took his life."
according to reports, rescue crews on jet skis and boats frantically hunted for the swimmer before human remains and parts of a wetsuit were recovered.
Shocked witnesses claimed the swimmer was attacked by a 15ft great white.
Lawrence Chlebeck, of Humane Society International, said the ferocious attack was incredibly rare.
"The vast majority of shark bites are a "one and done" occurrence. This is a very unique, and unfortunately tragic, situation."
Simon Nellist was training for the Malabar Magic Ocean Swim - which was due to be held on Sunday but has since been cancelled.
The event director Robert Lloyd, who confirmed it was now cancelled, said: "The organising committee extends our thoughts and prayers to the family of the swimmer who was so tragically taken yesterday.
"Out of respect for the swimmer and his family and following wide consultation with Randwick Council and experienced senior Surf Life Saving personnel, we believe that cancelling the 2022 swim is appropriate."