Dark Shape Swimming
A Stone Age painting
on a Sahara boulder:
a shadowy shape that swims
on some ancient river.
With no weapon, and no plan,
Neither at rest nor hurrying,
the swimmer is parted from his shadow
which is slipping along the bottom.
He has fought to get free
from millions of sleeping leaves,
to make it to the other shore
and join his shadow again.
- Tomas Tranströmer 
This poem, written in the 1950s, may reference images in a Wadi Sura cave, on the Egyptian border near Libya - the Cave of Swimmers. 
 From: The Half-finished Heaven: the Best Poems of Tomas Tranströmer, selected and translated by Robert Bly, 2001, Graywolf Press
 Cave of Swimmers figures prominently in the 1992 book The English Patient and in its 1996 film adaptation. The cave shown in the film is not the original but a film set created by a contemporary artist. Fame has taken a toll as an increase in visitors has increased damage to the cave’s paintings.