It looks like a metaphor, but it's not:

I see
the sea
shrink,
then shrink again,
and I
float farther
from the invisible shore.

(Shams Langroodi, "I See the Sea ...", tr. Sholeh Wolpé)

The shrinking of the Caspian Sea ... although the page I found the satellite photo on says the following:

Along with increasing pollution, the Caspian Sea has also seen its water  level fluctuate in past decades, at least partly due to human activity.  As dams were constructed on rivers feeding the Sea its water level fell  during the 1960s and 1970s, leading to construction on newly exposed  shorelines. But since the late 1970s the water level began to rise again  and has now risen by around 2.5 metres. Today it has stabilised and may  even be falling again.

I See the Sea