What is the theme in A History of the World in 10 1/2 Chapters by Julian Barnes?

One major theme in A History of the World in 10 1/2 Chapters is the sea. The sea has a place in each of the stories. As the sea is the greatest enigma on earth, it is a paradox in that it can be gentle and beautiful or violent and ugly. Its creatures are too vast to be counted, which is illustrated in "The Shipwreck." The crew of the Medusa first encounters a school of porpoises and later experiences the great strength of a deadly shark. The sea gives life to thousands of species of creatures, yet it cannot or will not support mankind.