Around the world, many people have to walk long distances to find a water source and others have to wait in long lines and pay large percentages of their income to secure any water at all, explain Damon and Gary White , who, along with Damon, co-founded the non-profit organization Water.org and the non-profit impact investment fund manager WaterEquity.

Indeed, 2.1 billion people lack access to safe, readily available water at home, according to a July 2017 report from the World Health Organization and UNICEF . That's roughly equivalent to three out of every 10 people, according to the report . Of those, 844 million people lack access to basic drinking water service. Further, 4.5 billion people around the world lack access to safely managed sanitation, according to the same report. That's roughly six in 10 people. A lack of access to clean water and sanitation is resulting in children dying from diarrhea and the transmission of diseases including cholera, dysentery, hepatitis A and typhoid.

"The potential it robs people of, right?" says Damon. "If you are a little girl who now can't go to school because you are in charge of water collection for your family, and you are spending your entire day scavenging for water, what kind of outcome can you expect for your life? Certainly you are not going to live up to your potential."

"You have a million people dying a year, just completely needlessly, because they lack access to clean water," says Damon , speaking to CNBC on Thursday, the 25th annual World Water Day , which serves to call attention to the problem.

Matt Damon is best known as an actor and Academy Award-winning screenwriter. But he's also the co-founder of two nonprofits working to end the world's water crisis.

"Today, 200 million hours will be spent by women and girls walking to collect water," says White, speaking to CNBC. "People are paying up to 25 percent of their income just to get dubious quality water that they can bring back to their home."

Women and children spend 258 M hours every day collecting water, but they could be doing so much more. Less time getting water means more time for work, school, play, family and life.

To work to solve this crisis, Damon and White came together in 2009 to launch Water.org, a non-profit that works to provide access to clean drinking water in 13 countries around the world: Ethiopia, Ghana, Kenya, Tanzania, Uganda, Asia, Bangladesh, Cambodia, India, Indonesia, Philippines, Brazil, Honduras and Peru. Water.org helps people gain access to clean water and sanitation by teaching, training and guiding local micro-finance institutions to make loans for providing access to clean water and sanitation.

"Gary kind of had this insight years ago," says Damon to CNBC.

This #WorldWaterDay donate to @Water and give families water and time for joy, hope, opportunity and life.

"The municipality is piping water underneath their feet, they are just not connected to it.... So if you could front them the money for a connection to the system that exists, you are buying their time back. They can work at a job they will get all those hours back that they are waiting in line or all that income back that they are wasting that the middle class wouldn't have to pay comes back into that household. And so it was this idea he had to apply the concepts of microfinance to the water space and it just was a brilliant idea. These loans pay back between 97 and 99 percent," says Damon.

In 2016, Damon and White launched an impact investment fund to provide capital to these microfinance institutions they were educating with Water.org. In 2017, the impact investment management arm of Water.org became a separate nonprofit, WaterEquity. Currently, WaterEquity is raising money for a $50 million fund, seeded by companies, institutional investors, foundations and wealthy individuals.

The goal of the investment fund is to get a 3 to 3.5 percent return (plus principal) to investors — "so that's better than a municipal, it is better than treasuries," Anne Finucane, a vice chairman at Bank of America, which made a $5 million zero interest loan to WaterEquity's fund, told CNBC Thursday.

For millions of low-income Indonesian families, water connections are unaffordable without financing. With small loans, women are empowered to give their families water at home. Less time getting water means more time for work. Donate to @Water and give time. #WorldWaterDay

The funds take the money, invest it through these local microfinance organizations and then return the principal with the interest to the lender.

"We take those funds and invest them in enterprises that serve the poor in terms of their water and sanitation needs," says White. "The basic math on it is that every million that comes into the fund, over the seven-year life, 100,000 people get access to water or sanitation.... It is a truly sustainable and scalable way to connect impact investors all the way down to poor women at the household level so that they can solve this problem."

Taken together, Water.org and WaterEquity have given access to clean water or sanitation to more than 10 million individuals around the globe.

Given a chance, people are able to take the access to water and really turn their lives around, benefiting themselves and their families. White uses a woman named Mama Florence from Uganda as an example.

"She took out a water credit loan and has a pump and water tank to store water in now, and she took that opportunity and starting selling water to her neighbors," explains White. "She wanted to send her grandkids to school — that was the impetus behind all this.

"And then she went from doing that to growing some vegetables, and then she would feed some to some pigs that she had purchased to raise, and then she used the water to start making bricks and selling those. And then she built some small rooms where people could come and rent. So She just used water and this loan as a way to really develop her own life and get her grandkids into school."

— Video by Mary Stevens

See also:

How Charity: Water's founder went from hard-partying NYC club promoter to helping 8 million people around the world

Why this Harvard grad has spent a decade making maxi pads out of banana fibers

The US wastes 62 million tons of food a year—this Howard Buffett-backed start-up has a solution