However, there was one small problem. The model-turned-actor could not swim.
"To be honest, I'm not a sports lover and don't like to do exercise," he told Young Post.
Yet Lee didn't let this hold him back. He had been dreaming of having a career as an actor since he was a child. So he took lesson to learn how to swim
"I spent one and a half months doing intensive training for the part - and learned how to swim," he said.
All his hard work paid off. From tomorrow, Hong Kong cinema-goers can see him starring in the romantic drama, No Breathing.
Lee plays the central character, Woo-sang, in the movie that focuses on competitive swimming.
Lee said : "I started to dream about becoming an actor at an early age. But, for some reason, my talent agency arranged modelling jobs instead. So I started out as model."
He began modelling when he was only 16 years old. Earlier this year, Lee got his acting break with roles in the popular TV dramas, School 2013 and I Hear Your Voice.
His latest project, No Breathing, provides a fun mix of action, romance and friendship.
Lee's character, Woo-sang, is a top swimmer who suddenly faces great challenges - yet never gives in to failure. Woo-sang has been kicked out of the national swimming team after getting into a fight with a foreign swimmer. He must try to earn his place back in the squad.
He meets Won-il (Seo In-guk), who is competing with him for a place in the team. To make things worse, the two young swimmers are also chasing the same girl, budding singer Jong-eun (Kwon Yuri); Kwon is part of the nine-member group, Girls' Generation
Seo In-guk (left) and Lee Jong-suk play rivals and friends.
To try to achieve the look of top swimmer, Lee went on a diet. He said the experience was painful because he loves eating.
"I couldn't eat the thing I love the most - streaky pork," he said. "After I finished the filming, I ate tons of meat. Now I have gained 5kg!"
After living the life of an athlete, he also gained an understanding of the determination it takes to win medals. Lee hopes the movie will offer one important message to Hong Kong youngsters.
"If you have found the thing that you want to do, make it happen," Lee said. "Pursue your dream without any hesitation.''
Lee discovered he had something in common with his film character. "I don't have a very close relationship with my father," he said. "I remember the first time that I told him I was going to be an actor. He did not like the idea."
Yet over time, Lee has proved himself. "My father has noticed my hard work over all these years, and he finally supports what I do," he said. "The same situation happens to my character in the movie."
Lee, 24, believes he's still too young to offer too much advice too other people. "But I do believe it's very important to set a goal - and fight for what you want while you're still young,'' he said.
Lee's belief in always doing his best makes him a role model for many young people.
"Being an actor, I feel like I'm finally living my dream right now. I'll continue to work really hard in my career."
The young actor is also looking forward to returning to Hong Kong - if he receives any new invitations. We're sure he will.
No Breathing opens on December 12.