Seventy per cent of our planet is covered by one huge, continuous body of seawater – the ocean. It holds 1.35 billion cubic kilometres of water. Nearly half of the ocean is more than 3 kilometres deep. The deepest known point of the ocean is in the Mariana Trench, 11 kilometres below sea level. But there may be deeper points that we have not seen, as we have only explored five per cent of the ocean to date.

The government of Canada suggested the idea of World Oceans Day at the Earth Summit in Rio de Janeiro in 1992. In 2008 the United Nations officially recognised the date and it has been growing ever since, from 100 events in 2008 to over a thousand events in more than 120 countries ten years later. The day is celebrated in a variety of ways, including special events at aquariums and zoos, beach and river clean-ups, school activities, conservation programmes, art contests and film festivals.