Over weekends, and possibly during the week, you will see scenes similar to this one dotting the Han River.
The long walk from Donjak Station to Yeouinara will lead you along the Han. As you walk you will be passed by groups of cyclists. Some speed by on snazzy road bikes. Some are just out for a ride on their own bikes in normal clothes. Even the lost soul on a rented jalopy may pass you.
Just off the bike road you will see encounter men, usually sitting alone and well away from any other human. They all have about four fishing lines cast into the river connected to fishing poles, leaning on special stands. Most of the men are just sitting there, doing nothing. They don't read. They don't listen to the radio. They don't play on their phones. They just sit and wait.
I can't help but think that doing this, once you get past all the thought that will inevitably run through their minds and when that chaos settles down, then this will be a great form of meditation. I'd really like to try it some time.