Hollywood heartthrob Leonardo DiCaprio has been making headlines for his efforts on spreading the word about climate change; and in his latest documentary – Before The Flood – he seems to have taken some extreme measures to film the scenes.

According to filmmaker Fisher Stevens, who worked with DiCaprio on the new documentary, the 41-year-old actor survived a near-death experience while filming underwater.

"The second time we properly hung out together was in 2010 when I was invited to film [oceanographer] Sylvia Earle for a TED conference expedition to the Galapagos. Leo was on the expedition," Stevens told GQ in a recent interview before recalling the horrific incident.

He continued, "I was filming Sylvia [Earle] and I had this little easy camera to shoot underwater, and he was Sylvia's diving buddy, so I said, 'Would you film Sylvia?' And he said, 'Yeah, I love it, man, I love it,'"

Unfortunately, the expedition became all too scary when the Oscar-winning actor's oxygen tank began to leak.

"I was diving buddies with Edward Norton. So we go down and we see 300 Eagle Rays and Spotted Rays and it was an amazing dive. Leo bolts away with Sylvia, and Edward goes in front of me, and the next thing I know after 20 minutes, I'd lost them all. Then, I see Leo barely breathing, because Leo's tank was leaking oxygen, and Edward had to save him!"

While the incident was "pretty crazy", the 52-year-old actor-director revealed that it helped him bond with DiCaprio during that trip. "But he actually did get some film for me and it was good for a second, and then it got pretty shaky when he couldn't breathe. But, we really bonded on that trip."

Clearly, this is not DiCaprio's first brush with death as he has faced such horrific experiences in the past as well. Previously, a great white shark jumped into the actor's cage in South Africa, an engine "blew up" right before his eyes when he was aboard a flight to Russia, and he almost died when his parachute didn't open during a terrifying sky-diving experience.

In fact, DiCaprio's last major project, The Revenant, which won him an Academy Award, too took a toll on him. "[I was] enduring freezing cold and possible hypothermia constantly," DiCaprio told Yahoo! Movies. "I certainly don't eat raw bison liver on a regular basis."