Seongsan eup, South Korea offers 1 beach perfect for sunbathing, surfing, swimming, and more. Seongsan eup, Jeju do, South Korea, is known for Seongsan Ilchulbong, a UNESCO World Heritage Site and popular sunrise viewing spot. The best time to travel to Seongsan-eup, South Korea, is in late spring (May), when the average air temperature is around 18°C (64°F) and the water temperature is approximately 16°C (61°F). Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!