Once formed from the primitive Earth environment, the oceans and continents have been constantly moving, changing, and evolving at a rate perceptible only in geological time. Oceans are defined as much by the shape and features of the underlying seafloor and their cover of sediment and organisms, as by the water they contain. Ocean basins are born, expand, and contract; islands rise from the sea; and continents grow and divide. The discovery that the land–ocean crust, as well as the Earth’s interior, acts as one unified system led to the most recent great paradigm of the earth and ocean sciences—plate tectonics. ‘Ocean transience’ explains the origin and evolution of oceans within this paradigm.