Deep waters

When you look across the plane of the sea
you can’t see where there are shallow stretches.
So sea charts are meant a help to be
the guidelines that the sonar etches.

As paradoxical as it might sound:
the danger lies not in the deep
but where the shallow sands are found,
or stones near the surface sleep.

Deep waters run still with the currents below
which are normally hidden, but eventually show.