This is the 6044th most frequent Korean word.
서해상에서
"On the West Sea" or "in the West Sea area."
'서해상에서' specifies the location of the event as being in the West Sea region.
서해상에서 큰 폭풍이 발생했습니다.
A big storm occurred over the West Sea.
'서해상에서' is used to describe the location where the activity of fishing is taking place.
그들은 서해상에서 낚시를 하고 있었습니다.
They were fishing over the West Sea.
'서해상에서' here indicates the general area as being above the West Sea where the described phenomenon occurs.