Girl group SECRET released a behind-the-scenes video for their hit song "Yoo Hoo" on Monday.

In it, the four K-pop singers suffer through the fast-paced three-day film shoot on the island of Saipan.

The nearly eight-minute long clip portraying the making of the "Yoo Hoo" music video, shows SECRET staying upbeat as they dance about in the Saipan sun and get hustled from one place to the next.

When we shoot something [in a location like Saipan], it's all so picturesque," gushed SECRET's Jieun on the first day of shooting. "I like summer better than winter."

The tropical island paradise was formerly used in the popular South Korean dating reality TV show "Kko Kko Tour."

Once Jieun finished filming an early solo sequence, she expressed concern for her SECRET bandmates on what it would be like dancing outside when the sun was higher in the sky.

"They said the hottest part of the day in Saipan is when we're going to film the dance scenes," she said in Korean with a twinge of concern in her voice.

SECRET's Hana, also filming a solo sequence, felt concerned as well.

"It's okay now," she said. "But later, when we're jumping around, I think we'll be sweating."

Yet the girls of SECRET made it look easy, keeping their irresistible charm afloat even in the afternoon tropical sun.

But when the shooting was over on day one, you could tell they we exhausted.

"The first shoot is over. I'm so happy," Hyosung shouted after her first day on the "Yoo Hoo" music video set had ended.

But the look on her face soon changed from relief to pain, as she looked ahead to the next two days.

"Tomorrow is going to be hard," she groaned. "And the day after that is going to be even harder. Big problem. And I'm hungry, I want to eat."

But when the next day came, and even the day after that, Hyosung and the three other members of SECRET continued to deliver the irresistible performances that helped make "Yoo Hoo" a runaway success.

And when the three-day shoot wrapped with the video's campfire scene, the girls were ecstatic.

"It was so hard!" Hyosung said through coughs as the campfire smoldered around her and the wind blew smoke into her eyes. "But it was for the fans.

Jieun got a little emotional as she thanked the group's supporters at the end of the behind-the-scenes video.

"Three years and six months [feels like] not that long ago," she said. Thank you for being with us for that long time."

See the behind-the-scenes video for SECRET's "Yoo Hoo" with English subtitles RIGHT HERE: