Dumujin is Baengnyeong's showpiece: a northwest coast of pale cliffs and rock formations cut by waves, wind, and rain. Korean tourism material likes to compare it to Geumgangsan on the sea, which is a large claim, but the coastline does have the hard, sculptural look that makes a boat trip worthwhile.
You can see parts of Dumujin from land along the port road, but the coast makes most sense from the water when cruise boats are running. Weather matters here; rough seas can cancel trips.