I take the beach as the border
In its place in the order
Of Land. Beach. Sea.
It separates the earth
Twixt the water and the turf
The sand boundary.
The water it fights
Through the day and the night
To steal the land back inside
But each time before
It has had to withdraw
The moon pulls back the tide
With sand seaweed and stone
The beach stands alone
In holding back the waves
So castles, they fall
Yet all through it all
The beach never quite caves***

https://harryisapoet.blogspot.com/2017/03/beach.html