The earths oceans have been a mystery for many centuries. Combined, they cover 71% of the planets surface or an area of some 361 million square kilometres. Nearly half of the world’s marine (oceanic) waters are over 3,000 metres (9,800 feet) deep.

All of our planets oceans are connected to one another but retain their individual activities and behaviour. Because of their connection, they are often referred to as the ‘world ocean’ or ‘global ocean’, the same water is circulated throughout them all.

The various oceans around the world are divided up by their continents and archipelagos.

The major oceans are (in descending order of size) the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, the Southern Ocean (in the Spring of 2000, the International Hydrographic Organization delimited this new ocean, the Southern Ocean – it surrounds Antarctica and extends to 60 degrees latitude) and the Arctic Ocean (which is sometimes considered a sea of the Atlantic).

Smaller regions of the oceans are called seas, gulfs, bays and other names. These smaller seas are not directly connected to the worlds oceans, but exist between connected countries throughout the world and connect only to the large oceans by small inlets and outlets such as channels, canals and estuaries. Some have no tides and some are very condensed with salt that they sometimes resemble lakes such as the Mediterranean Sea and Dead Sea.

The largest seas are the South China Sea, the Caribbean Sea, and the Mediterranean Sea.

Beneath the worlds oceans lie rugged mountains, active volcanoes and bottomless trenches, around bays there are shallower waters which lap sloping areas called ‘continental shelves’. The deepest part of the ocean is called the ‘Abyss’. The Abyss contains plains, long mountains ranges called ‘ocean ridges’, isolated mountains called ‘sea mounts’, and ocean trenches which are the deepest parts of the oceans.

Take a dive into the depths of our planets amazing but mysterious oceans and seas