It was a chance encounter that led Professor John Anthony Cherry to study groundwater contamination - a field which few thought would be important - back in the 1960s.
Since then, Prof Cherry, 75, who is this year's Lee Kuan Yew Water Prize Winner, has been making important contributions which have changed the way groundwater is being studied and managed around the world.
He was here last month for the Singapore International Water Week, where he received his accolade from Prime Minister Lee Hsien Loong.
The award recognises individuals or organisations that have contributed to solving global water challenges through innovative technologies, policies or programmes.
Groundwater, which can be found in spaces between soil particles and fractured rock underground, makes up about 95 per cent of the earth's usable fresh water.
However, it can be contaminated by agricultural practices or energy production such as shale fracking - the process of fracturing shale rock underground to release natural gas.
Singapore has a challenge that is very similar to other countries'. The challenge is water security. Groundwater is basically stored under the ground. It's just sitting there. But it takes sophistication to use groundwater to get security.
PROFESSOR JOHN ANTHONY CHERRY
Among Prof Cherry's contributions is his finding that contaminants found in aquitards - layers of clay that restrict water flow underground - can spread. Before his discovery, it was thought that such contaminants would spread only with the flow of water.
In 1976, he came across some measurements from an aquitard which he could not understand. It was only later, when he read a paper by a British hydrogeologist, that it struck him that the water underground was "fossil water", tens of thousands of years old.
He said: "One of the practical implications of this is if you decide you want to bury some hazardous waste down in the ground, the safest place to bury it is in an area where you have fossil water.
"Because if the water has moved so slowly... (and) if you can bury your waste there in the right way, you would have basically excluded it from the biosphere."
"And that is now what most countries want to do with their high-level nuclear waste."
In 1997, he and his colleagues also began studying a sandstone mountain near Los Angeles, which had been found by the United States government to be contaminated with a kind of industrial cleaning chemical.
The site had been used to test rocket engines. He said: "If the engine performed well, they would hose it off with these cleaning fluids.
"As it turns out, nobody knew at that time - in the 1940s to 70s - that the cleaning fluids would go down and infiltrate the rock.
"Many were very fearful that these chemicals would actually seep out under their cities."
Thankfully, his team found that while the chemicals had gone to depths of 500m, they had not spread very far and hence did not pose any threat to residents living around the mountain. The chemicals were also found to have stopped spreading.
The project is ongoing and the team is trying to find out if the chemicals are degrading.
Prof Cherry's foray into the field of groundwater contamination began with a chance encounter.
In 1967, when he was working at the University of Manitoba in Winnipeg, Canada, he met a female undergraduate who changed the course of his career. Hardly anyone knew anything about groundwater contamination at that time.
It turned out she had been studying radioactive waste buried in pits by a nuclear research facility and approached him to continue studying them as she had to leave Canada that summer.
"She discovered that there was some leakage of radioactivity. That became a great concern of hers," he said, adding that she thought he should feel "ethically obligated" to do the research.
"I explained: Well that's not the type of research I've ever done. Groundwater contamination isn't something that I was interested in and, at that time, nobody else was. But she was very insistent," said Prof Cherry.
While his venture into groundwater contamination research was a coincidence, water was always around while he was growing up in Ottawa, Canada. His mother would take him to a cabin on a freshwater lake during the summer and he would spend time canoeing and exploring the area.
When he was 15, his parents, who were documentary film-makers, moved back to Saskatchewan, where they had come from.
He said: "They were from a dry part of Canada, and some of the films were about water.
"I must have taken in the concern about water because they were from a world where people suffered in the 1930s when there was a big drought."
He is now the distinguished professor emeritus in the Department of Earth and Environmental Sciences at the University of Waterloo in Ontario, Canada. A current project is to build wells in rural villages in China so that people there can have access to clean water.
Groundwater contamination is an issue in such villages as bacteria from animal and human waste can seep underground and contaminate very shallow groundwater.
Like other groundwater experts, he is of the view that the most secure water of all is groundwater because events such as droughts cannot affect it quickly.
Singapore has relatively abundant rainfall and the opportunity to use groundwater as a secure access to water, he said. The key is to develop good monitoring networks so that the authorities know how best to tap on it, he added.
In 2013, national water agency PUB carried out exploratory studies to see if Singapore's groundwater could be extracted for use on a regular basis, or during periods of drought.
In May, it announced plans to install more monitoring wells and sensors around Singapore so that the groundwater system can be better understood.
"Singapore has a challenge that is very similar to other countries'. The challenge is water security," said Prof Cherry.
"Groundwater is basically stored under the ground. It's just sitting there. But it takes sophistication to use groundwater to get security."