The oceans have always been oceans.

I had fought on behalf of man against the sea, but I realised that it had become more urgent to fight on behalf of the sea against men.
From an interview on the 50th anniversary of his voyage, when asked about his avid support for environmentalism in later years.

Let us suppose, that the Old and New worlds were formerly but one continent, and that, by a violent earthquake, the ancient Atalantis [sic] of Plato was sunk ... The sea would necessarily rush in from all quarters, and form what is now called the Atlantic ocean.

The ocean ... like the air, is the common birth-right of mankind.

The sea is the source of water and the source of wind; for neither would blasts of wind arise in the clouds and blow out from within them, except for the great sea, nor would the streams of rivers nor the rain-water in the sky exist but for the sea ; but the great sea is the begetter of clouds and winds and rivers.

This long run is a misleading guide to current affairs. In the long run we are all dead. Economists set themselves too easy, too useless a task if in tempestuous seasons they can only tell us that when the storm is long past the ocean is flat again.

We may conclude, that the flux and reflux of the ocean have produced all the mountains, valleys, and other inequalities on the surface of the earth; that currents of the sea have scooped out the valleys, elevated the hills, and bestowed on them their corresponding directions; that that same waters of the ocean, by transporting and depositing earth, &c., have given rise to the parallel strata; that the waters from the heavens gradually destroy the effects of the sea, by continually diminishing the height of the mountains, filling up the valleys, and choking the mouths of rivers; and, by reducing every thing to its former level, they will, in time, restore the earth to the sea, which, by its natural operations, will again create new continents, interspersed with mountains and valleys, every way similar to those we inhabit.

Who that has ever visited the borders of this classic sea, has not felt at the first sight of its waters a glow of reverent rapture akin to devotion, and an instinctive sensation of thanksgiving at being permitted to stand before these hallowed waves? All that concerns the Mediterranean is of the deepest interest to civilized man, for the history of its progress is the history of the development of the world; the memory of the great men who have lived and died around its banks; the recollection of the undying works that have come thence to delight us for ever; the story of patient research and brilliant discoveries connected with every physical phenomenon presented by its waves and currents, and with every order of creatures dwelling in and around its waters. The science of the Mediterranean is the epitome of the science of the world.

Xenophanes of Kolophon ... says that ... [t]he sun is formed each day from small fiery particles which are gathered together: the earth is infinite, and is not surrounded by air or by sky; an infinite number of suns and moons exist, and all things come from earth. The sea, he said, is salt because so many things flow together and become mixed in it...