The Singaporean tourist had jumped into a 4m-deep pool at the bottom of a waterfall in a park in Pahang, Malaysia.
But he got into difficulties and started struggling in the water.
When Malaysian tour guide Kevin Tan Chew, 42, saw his client in trouble, he immediately swam to the man's aid.
Mr Tan managed to rescue the Singaporean, but at the cost of his own life.
The tragedy occurred at the secluded Perting Pandak Waterfalls near Bentong, about 70km from Kuala Lumpur, on Saturday.
Visitors have to trek about 45 minutes to get to the waterfalls, also known as Lata Hammers. The water pours into a pond about the size of an Olympic swimming pool.
It was to this idyllic setting that Mr Tan and his partner, Mr Amos Ho, 29, took a group of 10 Singaporeans on that fateful day.
The two adventure guides run OpenSkyUnlimited, a small outdoor adventure company which they founded.
Recalling the tragedy, Mr Ho told The New Paper in a phone interview on Tuesday that it began as a routine trip to the waterfalls with their Singaporean clients.
After they arrived at the Lata Hammers recreation centre, everyone had fun in the water. The waterfall pool was deep enough for the tourists to jump into from rocky outcrop.
Then one of their clients jumped in and got into difficulties because of the swirling currents.
Mr Ho, a former investment banker, said: "He was in the water. The pool was pretty deep, about 3m to 4m.
"There was some current around and he tried to swim against the current but he couldn't. He panicked and the more he panicked, the more he went under."
At the time, Mr Ho was about 100m further down from the pool, but Mr Tan realised their client was in danger and went to his aid.
"He is a trained swimmer and lifeguard. Kevin did what he was trained to do," Mr Ho said. "He did what he could to save the person's life while he risked his own life."
He said Mr Tan managed to push the client to the rocks but he himself disappeared into the water soon after.
"The client managed to hang on to the rocks. Everyone was on the rocks and after a moment, they couldn't see him."
He said they shouted out to Mr Tan but there was no reply.
One of them ran towards Mr Ho and shouted for help, saying "Kevin was underwater" and they could not see him.
Mr Ho said: "I was then about 100m further down and I ran up. By then, a couple of minutes had lapsed.
"I went in and pulled him out. I gave him CPR (cardiopulmonary resuscitation)."
By then, Mr Tan had been underwater for more than five minutes, he said.
"Some people went up to the parking area several metres away, where there was reception (for mobile phones) to call for help."
He said the rescue team arrived some three hours later because of the difficult access through the rough terrain.
Bentong district police chief Superintendent Mohamad Mansor Mohd Nor told Malaysian media that Mr Tan, who is from Petaling Jaya, near Kuala Lumpur, had taken a group of Singaporean tourists, comprising five adults and five children, to the waterfalls.
Malay newspaper Sinar Harian reported the police chief as saying that when the group arrived there, many of them were swimming in the area.
"At about 12.30pm, one of the tourists was believed to be drowning and Kevin went to save him. The 35-year-old tourist was saved but Kevin drowned instead," he said.
Mr Tan's body was taken to Bentong Hospital for post-mortem.
When asked how Mr Tan's family was coping with his sudden death, Mr Ho said: "They are coping okay."
He also said that he was coping "okay", but his distraught voice gave him away.
Mr Tan's funeral was held on Wednesday.
On June 1, a 22-year-old Malaysian also drowned while saving his friends at the same pool.
Mr Ahmad Dasrif Mohd Zaki from Balakong, Selangor, tried to help two of his friends who had been swept away by strong currents.
Although they were saved, Mr Ahmad Dasrif was himself swept away by the currents.
The victim's body was found a day later, face down beside a log in waters 4m deep and 2m away from the spot he was last seen.
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