She may have completed three triathlons, but when Ms Silvia Hajas plunged into the sea off East Coast Park to help four struggling boys, it was a leap of faith.
"I'm not a lifesaver; I didn't know whether it was going to work," she told The Sunday Times in an interview at her Costa Del Sol flat on Friday, seated with a view of the beach where the tragedy struck around noon last Monday.
When the 47-year-old housewife heard cries of the children in distress, her maternal instincts kicked in, and she leapt into the churning water - swimming out 50m time and again, ignoring her screaming muscles and thumping heart as she pulled first one boy, then two, then three, to safety.
With the first boy unable to swim, she felt all of his weight on her as she held him up above the water and pulled him back to shore with her right arm. "Everything was on my left arm and my legs kicking to propel me forward," she said.
Despite the adrenaline pumping through her veins, she found herself exhausted by the time she went back for the second boy. She yelled at him to flip onto his back in a floating position, but to no avail.
This made her life-saving efforts all the more difficult, as she could not hold him up above the water for long. At times, she would let him go momentarily to catch her breath.
Check out place before wading in
Before swimming in open waters, it is important to scout the environment, says swimming instructor Desmond Ho.
First, find out the depth of the waters by walking along the coastline. "You need to know where you can stand and where you cannot," said Mr Ho, who has 27 years of coaching experience.
"At East Coast Park, there are some areas where the sea floor can suddenly drop in depth. Start out at the shallow parts first, near the coastal line, before going out farther," he said.
It is also necessary to know whether the current is flowing inland or out towards the sea, he added. In areas where there is water drainage, the current could flow outwards.
"If you are swimming with the current, the water can help take you to where you want to go. But, if you are swimming against it, you will have to do more kicks and keep yourself as close to the top of the water as possible," said Mr Ho.
To ensure you are swimming in the right direction and have not drifted too far from the shore, use a landmark such as a lamp post or tree to gauge your position.
If you get tired or cramp up while swimming and cannot reach the sea floor, the best way to recover is to flip on your back and float, he said. But, in open waters where there are waves, this might not be easy during high tide, he noted.
"Men might also find it more difficult to float on their backs compared with women, due to their differing body structure."
If you notice someone drowning, call for assistance first. Then, look for a rescue device nearby to use if you are an adept swimmer.
"I knew I wouldn't let him go very far. I would let him go, but my hand was always nearby to pull him back up so we could keep going."
Meanwhile, her daughter stood on the shore, too afraid to look. "I was worried my mummy wasn't going to come back," said Trinity Neilson, eight, who is home-schooled. She and her mother had just arrived to admire the view and collect rocks for her geography project when the boys yelled in distress.
When Ms Hajas returned with the second boy, exhaustion had kicked in and she started to fear for her own life. She knew she would not be able to save the remaining two boys alone, and started asking for help from passers-by. A man who looked like he was in his 60s said he could not swim, so she turned to another man in his 50s.
"I remember the sense of desperation when I looked at him and asked if he could swim. When he said yes, I was practically begging him to help me, saying I can't do this on my own," said the Australian national who has lived here for six years on a dependant's pass.
DESPERATE FOR HELP
I remember the sense of desperation when I looked at him and asked if he could swim. When he said yes, I was practically begging him to help me, saying I can't do this on my own.
MS SILVIA HAJAS, on asking a passer-by to help with the rescue.
The man found a rescue float nearby which they used to reach the third boy. She said: "The boy was remarkably calm, and I felt so relieved when I saw him floating on his back. I knew he was going to be okay, even if it was going to take us a bit longer to get to him."
But by the time she went back into the water for the fourth boy, he had disappeared under the waves.
Muhammad Suhaimi Sabastian's body was found three hours later, at 3.33pm, by the Singapore Civil Defence Force's Disaster Assistance and Rescue Team. Suhaimi, 12, was a student at Jurongville Secondary School, along with the other boys. They were swimming after an exam paper that morning.
That night, Ms Hajas kept replaying the events in her mind, analysing what she could have done differently that would have saved Suhaimi's life. She wondered if using the rescue device earlier would have saved him.
"Mother's Day is around the corner and I can't imagine how his mother would be feeling.
"The practical side of me knows that I've saved three boys, but the emotional side of me is never going to be able to let go of that one boy I didn't manage to save," she said.
Three days after the incident, she returned with her daughter to the scene - about a 10-minute walk from their home. The view was just as beautiful as it was before, except now, Ms Hajas saw the water differently. Beneath those calm waves, she envisioned turbulent currents.
She told Trinity that regardless of the drowning, the sea was not the enemy. "You can't be afraid of the water. You have to face it front on. It's like the old saying: 'If you fall off a horse, you got to get back on'."
Mother and daughter will be taking part in an open-water race next weekend in Bintan.
The tragedy also stunned her husband John, 45. For a few days, he had difficulty coming to grips with the possibility of losing his wife of 14 years.
"But I wouldn't want her to have done anything differently," said Mr Neilson, who is head of technology risk at DBS Bank.
Ms Hajas has received much support from the public - more than 15 strangers have sent her private messages on Facebook.
These messages have helped her in the healing process, she said.
She hopes that by sharing her experience, more parents will be aware of the importance of sending their children for swimming lessons - not just for the sport, but for the critical lifesaving skills.
"It's a life skill that could potentially save your life or the life of somebody you care about, or a stranger in trouble," said Ms Hajas.
The family will be spending Mother's Day today at Sentosa, as Ms Hajas and Trinity train for next weekend's race.
Trinity said that while her mother did not tell her what she was doing before she jumped into the water that day, she knew that mum was saving the boys.
"It's what my mum does. She's a superhero."