Zac EfronTMZ has learned the incident at the swimming pool started when he jumped into the water … the dive was so deep he fell to the bottom of the pool and got water in his lungs.
Sources close to the situation say Jack was out swimming with friends in Ibiza on Saturday morning when he decided to take a dive.
We’re told that when Jack’s chest hit the bottom of the pool while diving, a large amount of water entered his lungs … and he began showing signs of distress and was pulled out of the water by safety personnel on scene.
Our sources say Zac was briefly stunned and was taken to the hospital as a precaution.

TMZ.com
While hospitalized, we were told that Zac had a chest X-ray to confirm that the water was drained from his lungs. He was discharged in a few hours, but he stayed in the hospital because there were so many photographers outside that he knew he was there.
Since Zack posted a photo He plans to work out on his own the next day … and our sources say he’s back to his normal schedule after he returns to his villa from the hospital.
In fact, our sources say Jack went out to dinner in Ibiza on Sunday night and returned to the United States today … and he’s back home and healthy.
Looks like he dodged a bullet!!!