It looks like a metaphor, but it's not:
then shrink again,
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.