Young Japanese women are flocking to pools on summer evenings -- but not so much to swim as to shine on social media.

Women in their teens and 20s are putting on their bathing suits and heading to "night pools" at upscale hotels and other tourist facilities in major cities, where they spend time taking selfies with friends on inflatable tubes and sipping cocktails at the poolside.

"Night pools" all the rage among young women on social media

The night pool at Hotel New Otani in Tokyo opened for business on July 21. A DJ pumps out music in the background as partygoers revel amongst illuminated palm trees creating a tropical atmosphere. At 8,000 yen the admission fee is not cheap.

"It feels like something out of the ordinary, and I'm happy if I can post something on social media and can get more followers," said Hisami Okamura, a 22-year-old college student from Tokyo's Koto Ward who came to the pool with a friend. "I won't swim because my makeup and hair would get messed up," she said with a laugh.

Night pools got started back in 2001, but the surge in female customers only began in around 2014, thanks to social media.

"There are days when people have to wait as long as three hours for admittance," said the person in charge of the night pool facility at the hotel in Tokyo's Chiyoda Ward. "We never thought the advertising effect of social media would be this big."

At a poolside event staged by women's fashion magazine CanCam at the Tokyo Prince Hotel, women hold brilliantly colored balls with light-emitting diodes and try to look pretty for the camera as they float on giant inflatable tubes. The hotel expects a threefold increase in customers this year.

"Night pools" all the rage among young women on social media

Many women can also be seen taking selfies with the pool's surface illuminated in the background at the Hyatt Regency in Osaka.

In an internet survey conducted in March by travel magazine Jalan of 121 women ages 18 to 29, 44 percent, or nearly half, of respondents said they have gone out before "for the express purpose of uploading images to social media."

The magazine's chief editor, Nao Ohashi, said, "Social media is one tool young women can use in their self-productions. It seems that their motivation for uploading images is that they crave recognition."

As demand increases, tourist facilities are jumping on the bandwagon and offering cheaper prices than hotels.

Amusement park Toshimaen in Tokyo's Nerima Ward has brought back night pools for the first time in 30 years. The admission fee is 1,500 yen and business hours are extended until 9 p.m. The park's website shows an image of actress Marilyn Monroe pulling her legs into a 45 degree angle in a wine glass filled with blue liquid.

"During the daytime mainly families and students come, so this is a chance for us to expand our customer base," said a person in charge of the facility.

Laguna Ten Bosch, a multi-resort complex in Gamagori, Aichi Prefecture, central Japan, opened a new night pool event for the first time this year.

Theme park Huis Ten Bosch in Sasebo, Nagasaki Prefecture, which is holding events again this year after favorable reviews last summer, calls its luminous night pool "an adult hideaway."

According to the Japan Productivity Center, the country's domestic leisure market was worth 71 trillion yen (about $634 billion) in 2016, down 2 percent from the previous year.

But JPC senior researcher Takenori Shimura said because of social media, leisure activities among young women are on the rise.

"Young women are sensible in how they get their jobs done, and are inclined to enjoy leisure. They are also leading other age brackets in their use of social media," Shimura said.

The more young women get involved in novel leisure activities, he said, the bigger the economic impact.

"Night pools" all the rage among young women on social media