Before Peeta and Katniss broke box-office records, before Edward and Bella set tween hearts swooning, there was Jack and Rose.

Fifteen years ago, the youthful star-crossed lovers in 1997's Titanic – played by Leonardo DiCaprio and Kate Winslet – helped propel James Cameron's epic blockbuster into box-office history. The film earned $1.8 billion worldwide and scored 11 Oscars.

Now Titanic is sailing back into theaters on April 4, this time in 3D. To mark the re-release, which is taking place along with the 100th anniversary of the real sea disaster, PEOPLE spoke with Winslet and Cameron about their memories of the film – including a few surprises:

1. Leo almost passed on the role.
莱昂纳多差点错过这个角色。
The actor, then 21, was reluctant to take on such a traditional, romantic leading-man part. "His character doesn't go through torment, and Leo previously and subsequently in his career was always looking for that dark cloud," explains Cameron. "It became my job to convince him that it was a challenge to do what Gregory Peck and Jimmy Stewart did in previous generations, to stand there and be strong and hold the audience's eye without seeming to do very much. Only when I convinced him that was actually the harder thing to do that he got excited."

2. The water was warm (for a few reasons).
由于各种原因，当时的”海水“是暖的。
Cameron acknowledges that the seven-month shoot was intense – but says the soggy scenes weren't as hard on his actors as it appears on film. "The water in the tank was about 80 degrees, so it was really like a pool," he says. "All of the cold, frigid breath was added later." And what about reports that Cameron forbid his stars from leaving the water tank for hours at a time, even to use the bathroom? "Everyone could go to the toilet, but they were encouraged not to go in the tank – which I think was happening!"

3. Kate and Leo have a tough time watching the film today.
现在，凯特和莱昂纳多看这部电影有点别扭。
"My American accent is appalling!" says Winslet – who went on to earn an Oscar in 2008 for The Reader – of her breakthrough performance. "Here we are 15 years on, and I've learnt so much more, not just about myself but the job that I do and the world of film, and I look at myself in Titanic and I wish I could bring all this knowledge that I now have into that." As for DiCaprio, "I just saw Leo a few months ago and I showed him 18 minutes of the film converted to 3D," says Cameron. "We had a good reminisce and, of course, he was guffawing at what a kid he was in the movie. I think he hadn't seen it in a while and seeing it on a big screen, he was literally just snorting into his hands at one point."

4. Kate had a shaving emergency mid-shoot.
拍着过程中，凯特有过一次“剃毛危机”。
In the scene when Rose is about to jump ship, "there's a bit where Leo takes my hand, and because of the way Jim was lighting this particular shot, the light was catching all the little hairs on my arm," says Winslet. "He was like, 'Okay, we're going to have to shave your arm.' So we stop filming and the makeup artist has a Bic razor and some Gillette shaving foam. It was hilarious. That I really remember."

5. Leo and Kate hit it off instantly.
凯特和莱昂纳多很快就“进入状态”。
"They were very chummy and relied on each other quite a bit," Cameron recalls of his young stars. Although Winslet teasingly says that a boyish DiCaprio was "useless" during filming when it came to keeping a watchful eye on her, he did come through in a key moment. "When we did the underwater footage at the end, Leo was a certified scuba diver at that point and I was not," she says. "He really did look after me. He was totally brilliant – he wouldn't leave my side."