Shanhaiguan & laolongtou, are they separate walls?

Hello! I want to visit the Great Wall at Shanhaiguan because I was told that its there where the wall meets the sea.
However, after doing some research, I've found LAO LONG TOU, which is the wall right by the beach, and its 4km south of SHANHAIGUAN.

So, now I'm a bit confused. Where do I go if I want to see the Great Wall by the sea? if the Wall is connected, can I only pay one a visit both? Or are they separate and I have to pay both?

If the answer is I have to pay twice, which part would you recommend me to see?

Thx!