An ocean is a large area of salt water between continents. Oceans are very big and they join smaller seas together. Together, the oceans are like one "ocean", because all the "oceans" are joined. Oceans (or marine biomes) cover 72% of our planet. The largest ocean is the Pacific Ocean. It covers 1/3 (one third) of the Earth's surface.
The smallest ocean is the Arctic Ocean. Different water movements separate the Southern Ocean from the Atlantic, Pacific and Indian Oceans. The Southern ocean is also called the Antarctic Ocean, because it covers the area around Antarctica.
The deepest ocean is the Pacific ocean. The deepest point is the Mariana Trench, being about 11,000 metres (36,200 feet) deep. The deep ocean is characterised by cold temperatures, high pressure, and complete darkness. Some very unusual organisms live in this part of the ocean. They do not require energy from the sun to survive, because they use chemicals from deep inside the Earth.
Colours of the Sea
Although many people believe that the oceans are blue because the water reflects the blue sky, this is actually not true. Water has a very slight blue colour that can only be seen when there is a lot of water. However, the main cause of the blue or blue/green colour of the oceans is that water absorbs the red part of the incoming light, and reflects the green and blue part of the light. We then see the reflected light as the colour of water.
The Ocean has its silent caves,
Deep, quiet, and alone;
Though there be fury on the waves,
Beneath them there is none.
The awful spirits of the deep
Hold their communion there;
And here are those for whom we weep,
The young, the bright, the fair.
Calmly the wearied seamen rest
Beneath their own blue sea.
The ocean solitudes are blest,
For there is purity.
The earth has guilt, the earth has care,
Unquiet are its graves;
But peaceful sleep is ever there,
Beneath the dark blue waves.
— "The Ocean" by Nathaniel Hawthorne