Dolphin watching

The black triangle slices
Through the concrete waves,
Like a prisoner
Sawing his way to freedom.
A flash of black back,
Rubbery and sleek.

Above in an alien world,
We patrol the light,
Pointing and clicking
And laying hands
On young shoulders,
Watching for a dark form
To break the cell roof.

Or are they the wardens of the deep,
On watch, lest those strange upside-down shapes
Crash through their crystalled palace?