A 5 letter word for seashore is beach.
I think perhaps the word you are looking for is "cove".
Shoreline indentation refers to areas where a coastline curves inward, creating a bay or cove. This indentation can be caused by various factors such as erosion, tectonic activity, or volcanic processes. Indentations in the shoreline provide unique habitats for marine life and can also affect coastal erosion and sediment movement.
Lumen
The indentation above the upper lip and below the nose is called the Philtrum.
This indentation is called the oral groove which leads to the gullet. See the link below for a diagram:
It's called an Indent, or Indentation.
A shoreline indentation is called a bay. It is a curved area of water partially surrounded by land, often less exposed to the open sea than a gulf.
The indentation in the top of the manubrium is called the jugular notch, also known as the suprasternal notch. This anatomical feature is used as a landmark for various medical measurements and procedures.
A concave mark is called a "dent" or "depression." It refers to an indentation or hollow area in a surface.
It is called the suprasternal notch. And it is mine.
Jersey Shore Soundtrack