This is the 17265th most frequent Korean word.
서해의
"Western Sea's" or "of the West Sea."
In this sentence, '서해의' acts as a possessive determinant related to '섬들' (islands), implying that the islands belong to or are located within the Western Sea region.
서해의 섬들은 아름답습니다.
The islands of the West Sea are beautiful.
Here, '서해의' modifies '풍경' (scenery), indicating that the scenery referred to is specifically that of the West Sea.
나는 서해의 풍경을 찍으려고 계획하고 있어요.
I am planning to capture the scenery of the West Sea.
In this sentence, '서해의' modifies '물고기' (fish), attributing them as being associated with or coming from the West Sea.