bborang 
Masian Beach is 25 minutes from Incheon Airport by taxi. Tidal flats, a west-facing sunset, clam digging for 10,000 won, and a free maglev that runs 10am-5pm. You need eight hours.
Coin lockers cost 2,000-3,000 won and staffed counters 4,000-10,000 won a day at Incheon Airport. The real price is time: up to 75 minutes on a bad day.
There is no direct public transport from Incheon Airport to Ganghwa Island. Drive or take a taxi, 50-60 minutes, and give yourself ten hours. Here is why it is worth it.
Yes, if you have more than five hours. Immigration alone can run past 90 minutes at peak. Here is the full arrival-to-gate timeline and the numbers that decide it.
A ten-minute walk from Unseo station, one stop from Incheon Airport. Clear gomtang or the spicy version, 11,000-12,000 won, with a photo menu by the door.