Cannon baaaaaaall!

Taking a page out of the Ron Burgundy pool party style book, Justin Bieber got wild at the pool, a la Anchor Man on Monday. No pool is safe when Justin is around!

Fresh from his headline-making trip to Ibiza, the Biebs is back in Los Angeles -- and has wasted no time posting his mischievous antics to Instagram.

In the video, the 20-year-old says to the camera, "Back in Cali, back in the studio ... time to get back to work ... but first ... CANNON BALL!"

All work and no play makes JB a dull boy!

Over the weekend, Selena Gomez's human kryptonite joined Kardashians, Kim, Kris, Kylie and even Kanye West, in the sexy Spain island for a birthday party for Givenchy fashion designer Riccardo Tisci last.

The pop star had quite the the blast in the Spanish city, that is, despite coming to blows with actor Orlando Bloom.

Rumor has it that round two of the Bieber-Bloom saga almost kicked off at Tisci's bday bash, but Bloom ended up leaving the party upon seeing Bieber's entourage. Well ... we've seen the "Boyfriend" singer's beefed-up entourage -- we don't really blame the Brit.

Uhh ... we're glad you're back Justin. Los Angeles is so much less interesting with you gone!