It's totally unrealistic, and probably insulting to the survivors. Instead of being shown as trained professionals going about their duties, they are portrayed as likable but incompetent, needing to be reminded to carry out basic duties by their brave, calm superiors. In the midst of battle, they pause for long speeches. And the heroes always manage to overcome multiple high-caliber rounds through the torso, using sheer strength of character to stand up straight despite severed spines and punctured lungs. Which implies that death or disability is a character flaw.
Canadian propaganda films, like "Hyena Road", or the "Combat Hospital" TV series, seem much better written.
However, the photography of Yeonpyeong Haejeonis beautiful, even more so considering the minuscule budget. Worth watching, if you turn off the subtitles and fast-forward through the worst parts.
Interesting technical bit: the North Korean patrol vessels shown in the film had old WWII-era T-34/85 medium battle tanks on their forward decks, acting as an armoured turret. I suppose that's a good use for a tank when the drive train finally dies, but the gun and traversing gear still work.