Growing up in Pennsylvania, near Philadelphia, going to Seaside Heights NJ was a summer staple. There were closer (and probably nicer) beaches, but I had family in South Jersey, so we could visit with them along the way. Seaside Heights had a classic, kitschy boardwalk/pier setup and a little beach you had to pay to get on. Unhealthy restaurants and little shops. There are a collection of motion-sickness tempting rides, such as the spinning thing pictured above. Apparently a radio dj runs the ride and makes taunting comments about the riders as he speeds it up to torture them more. Classic.
Imagine my grotesque delight at realizing that Incheon (which nicely fills the role of New Jersey in a Seoul/New York comparison) has its own Seaside Heights. Wolmi Island is a short bus ride over a bridge away from the main island of Incheon. Though its boardwalk is surrounded by rocks, making a beach visit impossible, the atmosphere was strangely familiar to that of those childhood summers.
Lots of seafood restaurants of varying quality, as well as street food. Wolmido has something Seaside Heights never did, but would surely covet: a corn dog covered in french fries. They also have crowded shops full of tacky summer gear.
Wolmido also has a nice park and a tiny mountain to climb. There is an observation tower with a cafe in the top, and several military monuments on the island. One full scale ship with little fountains spraying water around it.
I had a fun day of hiking and wandering the boardwalk. To go to the beach though, I had to go to a different Island.