The Atlantic is of course the cradle of imaginary civilisations, all the more imposing and fearsome and aweful for their imaginary status. It is raw water running in huge amounts, the same water that flooded through the gates at Gibraltar and drowned the plain that became the Mediterranean. There are no safe margins by which a ship might sail across the Atlantic forever within sight of civilised land.
The Indian, on the other hand, is the cradle of a hefty chunk of real civilisations, from the east coast of Africa up to the fractured lands we call the Middle East and Mesopotamia, and along the coast of the Indian sub-continent, the central feature of that ocean, and down the Kra peninsula to Singapore and beyond. It ranges from Port Elizabeth in South Africa to Adelaide in South Australia.
The Indian is a benign ocean, relatively speaking. This is why trade across the Indian was the most important trade of all for many centuries. The Atlantic is relatively turbulent, and if not for the wholesale theft of the New World's riches to pay for the Old World's luxuries, was not an encouragement to global trade.
Winchester makes one mistake. He points out how European and American talent in the arts and letters were inspired by the Atlantic to develop complex Romanticism. But the question must be asked: What other ocean did the Romantic soul have to write, sing or play music about? In overstating the case, he did his marvelous oceanic subject a great disservice.