Sir David Attenborough

could take pictures of coral reefs but could not explain why they harboured such a wonderful array of diversity.

we have changed the ocean so profoundly that the next hundred years could either witness a mass extinction of ocean life or a spectacular recovery

We began to think of the ocean in terms of five major connected basins: Arctic, Atlantic, Indian, Pacific and Southern – though the Southern Ocean wasn’t officially recognised as a distinct ocean basin until 2021.

Named after the two factors influencing the density of seawater, temperature (thermos) and salinity (haline), this system begins with the freezing of seawater in the far north and south of our planet.