PopUps: Bieber Bares His Butt on Instagram

Get it while it's hot! Or until it's deleted.

It's been a wild month for celebrity nudes on Instagram, with 52-year-old designer Marc Jacobs breaking the Internet last week for accidentally posting a nude to the social media site. Now pop star Justin Bieber is following suit -- though this is clearly no mistake.

The "Where Are U Now" singer posted a pic of him on what appears to be a boat in a beautiful location. But some of his 32.1 million followers may find something else more eye-grabbing than the deep blue serene water, the clear sky or the lush mountain in the distance -- Bieber's bottom.

The 21-year-old singer is fully nude in the pic and he's seen pointing to the mountain, adding the caption "look" to his photo, which currently has 1.4 million likes and over 420,000 comments.

Is his naughty pic on the way to being the most liked on Instagram? Kendall Jenner currently holds that honor, recently beating out her stepsister Kim Kardashian's record. A photo Jenner posted about six weeks ago, showing her laying down with her hair shaped into hearts, has 2.8 million likes.

The New York Daily News points out what is more surprising than Bieber in the buff (let's not forget his risqu� Calvin Klein ads) is that he's not afraid of being in the water. The pop star recently shared a photo of friend Joe Termini, who suffering a shark attack and had wounds on his chest.

"Exactly why I hate sharks they told us reef sharks don't bite," Bieber captioned the photo on Sunday.

Bieber hasn't said anything else about his butt shot, but after Jacobs made headlines for posting his rear on Instagram, the designer later gave a fantastic response.

"Yeah. I accidentally posted a pic of my bare ass and took it down," he wrote in an Instagram comment, replying to a fan. "I was flirting with someone I met on Instagram. Meant to send it by DM. Oops, my mistake. I apologize to anyone it offended. I'm a gay man.

"I flirt and chat with guys on line sometimes. BIG DEAL," Jacobs added.

This story is part of our special report: "PopUps". Want to read more? Here's the full list.