Staying at a hotel on the Thai island of Koh Samui in 2015, Meghan Kerrigan noticed the four bottles of water she was given every day were clogging her trash can with plastic. Outside her door, Chaweng Beach was smothered in rubbish.

It was then that she and two friends, brothers Ryan and Matthew Kohler, had a “light-bulb moment.”

“Instead of trying to solve the problem by cleaning the beaches every day, let’s go to what the source of the problem is, and take the plastic bottle away,” said Kerrigan, 31.

In 2016, the trio founded the startup Generation Water, based on the Thai resort island of Phuket.

They partnered with Marriott, the world’s largest hotel brand, in January 2017 to come up with a sustainable alternative to plastic bottles that would be commercially competitive and meet the needs of resorts and authorities.

Two years on, the South African-born entrepreneurs explained the workings of a pilot water plant at the JW Marriott Phuket Resort & Spa on Mai Khao Beach. There, in the sweltering heat, two water generators suck in air, whose vapor condenses into water when it hits cold coils.

The water drips into tanks, making 4,000 liters a day. It is filtered, minerals are added, and it is put into reusable glass bottles. These are placed into 445 guest rooms at the JW Marriott Phuket and neighboring Renaissance Phuket Resort & Spa.

The bottled water is also being trialed at two Marriott vacation clubs nearby.

The move is part of a wider effort on the holiday island to cut down on plastic bottles, which are rife in the hospitality industry and are a major problem in Asia and its travel hot spots.

In many parts of Asia, tap water is unsafe to drink, so hotel guests get complimentary water, mostly in plastic bottles.

As much as 60 percent of the plastic found in the ocean comes from five Asian nations, including Thailand, according to the U.S.-based nonprofit group Ocean Conservancy.

In 2017, the United Nations Economic and Social Commission for Asia and the Pacific organized a forum to encourage sustainable water management on resort islands.

On Phuket, which is half the size of Hong Kong, more hotels are being built, and water is already in short supply. Trucks navigate crowded roads as resorts without their own catchment area bring in water from reservoirs.

Phuket was the world’s No. 11 city destination in 2017, with 11.6 million international arrivals, according to global research company Euromonitor International.

To cope with the environmental impacts of this influx, nearly 70 hotels from the Phuket Hotels Association have pledged to cut plastic bottles and straws by the end of this year.

Since Marriott started producing its own water four months ago, it has stopped more than 100,000 plastic bottles from entering landfill or oceans, the chain says.

It plans to expand the project to all Marriott resorts in southern Thailand, handing out 4 million glass bottles.

Carsten Siebert, Marriott International’s director of operations for Thailand, Vietnam, Cambodia and Myanmar, said the company understands it has “a greater obligation to operate responsibly given our expanding global footprint.”

The chain has a goal to reduce water consumption per occupied room by 20 percent between 2007 and 2020.

The “water from air” technology uses 78 percent less energy than producing standard bottled water, has a lower carbon footprint and is about a third cheaper, Generation Water says.

“The good thing is that it starts to become financially affordable,” said Matthias Sutter, general manager at JW Marriott Phuket.

Nor does the system rely on pulling water from the ground, rivers or lakes.

“We don’t have to invest in land to secure our own water,” said Kanokwan Homcha-aim, corporate social responsibility manager for the same Marriott hotel.

Guests there have reacted positively since the bottled water was introduced in September, happy that “finally a big brand made a move,” she said.

They also like the taste.

Michael Lawson, a lawyer from Sydney sitting at the Sala Sawasdee lobby bar, said his children are “quite picky” about water. “But it’s very refreshing and they are fighting over it in the room,” he said.

Downstairs in the Siam Deli, teenage student Jeremy Frydman from Melbourne said it tasted better than tap water at home.

One challenge for Generation Water is explaining the science behind the technology.

Many guests ask about air pollution, for example. But the water collected is clean to start with, and the technology works even if the air is polluted because only its water condenses, not the air itself or its contaminants, said Ryan Kohler.

And with human activities emitting more greenhouse gases, the atmosphere is warming up, causing more water to evaporate, which further heats the air in “a vicious circle,” he added.

The water-from-air system helps reduce this vapor, said Kerrigan, adding that it has no impact on rainfall levels.

Thailand’s food and drug administration approved Generation Water last August, and the company is now expanding.

It is building a plant in Phuket, which will use solar energy to make “climate-positive” water, producing more than 20,000 liters of water per day by the end of the year.

Nine Marriott resorts on Phuket are in the process of signing up, along with 30 other hotels.

Generation Water is now eyeing the rest of Thailand, and is talking to hotels in Singapore, Indonesia, Vietnam and the Maldives, Kohler said.

It also sells smaller water production units that can be used in homes, offices, classrooms and on yachts.

The company’s goal is to stop 1 billion 500-ml plastic bottles from entering landfill and the oceans every year by the end of 2021 — equal to supplying 3,000 hotels of 250 rooms.

As for Marriott staff on Phuket, they have “no excuse now,” said Homcha-aim.

Their birthday gift from the company will be a reusable tumbler, which they can fill up with “water from the air.”