Usually you have to travel far to see the sea, but if there’s a cafe nearby where you can enjoy a cup of coffee while looking out over the sea and the bridge, I would recommend this place.
It’s a large cafe, and while it’s not open all night, it stays open late enough that you can enjoy the night sea even if you go in the evening.
On the way back, you could stop at a beach around Ganghwa-do to enjoy the sea, or take a drive and return — either would be fine.
How about visiting Eonkaeni Cafe for a cup of coffee while watching the sea?