The Gapyeong Ice fishing festival is an annual festival that can be reached fairly easy from seoul using public transit or the itx train. The festival costs about 25-30 dollars including train fare and entrance into the festival plus you get a 5000 won gift certificate for the vendors at the festival ( so the festival is actually 20-25 dollars and a 5 dollar gift certificate). The festival runs from early January to February.
How to get there itx easiest way:
take seoul transit to yongsan and buy a itx ticket at yongsan for Gapyeong station. There is an itx terminal and you just wait for your train to arrive. Once on the train enjoy the sights of korea and get off at gapyeong station. Once you exit the train station it is a 15 minute walk to the festival or a minute bus or taxi ride. Once you arrive at the festival buy your fishing pass and have a fun day fishing.
Types of fish you can catch:
I went to the festival in January 2015 and the only fish I seen getting caught was mountain trout. I assume the river was being stocked because the amount of fishers was pretty vast and many people were catching fish.
After your done fishing:
once you have caught your limit or have given up on fishing you can go to the food vendors and have your fish cooked or buy fish if you were unable to catch anything. The cost of getting your fish prepared varries on whether you want sushi or smoked fish. After you receive your fish you can enjoy a beverage and your fish.
walk or ride a vehicle to gapyeong station and ride the itx or subway back to your home station.