Castle in the sand

Today when I sit on that magical borderline
between grains of silicon dioxide and saltwater,
I dig out a little hole,
(kind of like an antlion's sandpit,
though there is a certain perversion that
the sand is the sand, but
the beach is not the desert)
I haven't so much as thought of digging a foundation
for a castle of sand, when
the waves sweep the sand level,
and the castle in the sand only becomes
the castle in the air.
But what struck me most wasn't the extinguished architecture,
but the fact that the waves gently, ferociously slapped everything even.
Castles of sand, houses, cities, happiness, sadness, anger,
well, people.
And the ancient voices doth spake:
Syrus: In the face of death all men are equal;
A Chinese sage: In the face of Truth, all are students.

(Me: In the face of tidal wave, run away.)