Park BoGum, the ocean swimming scene in ”Good Work” was real... ”It was really in the middle of the ocean”

Actor Park Bo-Gum revealed the behind-the-scenes footage of the ocean swimming scene he filmed in "Thank You."
On the 3rd, Netflix's official YouTube channel posted a behind-the-scenes commentary where they solved TMI and behind-the-scenes issues together.
The video, "Lee," was posted on the website. It features director Kim Won-seok and the cast including IU, Park Bo-Gum, Moon So-Ri, and Park Hae-Joon.
In the video, IU said, "This was a scene that Bo-gum had a lot of trouble with. The whole sequence."
Director Kim Won-seok said, "There were days when it actually rained. We shot the scene in Busan for two days and in Changheung for two days.
He explained, "Everyone worked hard. We shot it relatively early on, but both the writer and the actors were satisfied when they saw the edited version. They felt that all the hard work was worth it."
When IU said, "Bo-gum really swam in the ocean," Park Bo-gum replied, "People think it's CG (computer graphics)."
When asked when he became a good swimmer, Park BoGum joked, "Since I was born," and
IU exclaimed, "Is that a whale?" Park BoGum added, "The best part was that I could hear all the cheers from my seniors while I was swimming."
Moon So Ri, who saw this, said, "If that was the case, we should have sent him to the Olympics," and Park
Hyejun praised her, saying, "I'm good at it too, but you have great posture." Regarding the scene in the drama where Kwangshik climbs up the breakwater to embrace Ae-sun, IU said, "It was really cold, and when we hugged each other, I felt like I was in awe.
"We were shaking every time we touched each other," Park BoGum said.