Leonardo DiCaprio nearly drowned once

Speaking at the premiere of 'Before The Flood', director Fisher said: "The second time we properly hung out together was in 2010 when I was invited to film Sylvia Earle for a TED conference expedition to the Galapagos. Leo was on the expedition. I was filming Sylvia 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.'

"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 twenty minutes I’d lost them all. Then, I see Leo buddy breathing, because Leo’s tank was leaking oxygen, and Edward had to save him! It was pretty crazy. 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."

Meanwhile, Leonardo has endured a number of tricky filming conditions in the past, having famously eaten raw bison liver while filming 'The Revenant'.

Speaking of the meal, he said: "The bad part is the membrane around it. It's like a balloon. When you bite into it, it bursts in your mouth."