Daebudo is a large island off Ansan in Gyeonggi, now tied to the mainland by the long Sihwa seawall. It still feels like a west-coast island trip: mudflats open at low tide, seafood villages line the road, and sunset viewpoints look over the Yellow Sea.
The island is spread out, so a car or patient bus plan helps. The north has the seawall, the tidal power plant, Gubongdo, and the mudflat experiences. Farther south, museums, fishing villages, salt fields, and glass art stops make Daebudo more varied than a simple beach run from Seoul.
Come when the tide is part of the day rather than an afterthought. Low tide shows the flats and sea paths; evening brings the sunset views that make the drive worthwhile.