Castles in the Sand by Dorothy Baker Sea poem

I've built a castle in the sand
In less than half an hour,
With grim portcullis, and a moat,
And battlements and tower.

The seaweed banners wave, and when
I let the drawbridge down,
The knights come riding two by two
In armor Rusty Brown.

And ladies lean from Turrets high,
And watch them as they pass,
And wave their floating silk scarves,
As light and green as grass.

But see! Across the Shining Sand,
and me the sea
Creeps slowly to my castle walls,
Advancing stealthily.

No bugles sound a wild alarm,
No warders close the gate;
The knights and ladies disappear,
And all alone I wait.

For where my fairy fortress stood
And glistened in the sun,
There lies a heap of ruins now,
My work is all undone.