With a span of more than double the size of  landmass, the waterworld has always been a source of myriads of life forms. 

Obviously it is in this world where the first forms of animal life made their appearance. It was long long before they appeared on land. In that sense water world is an older habitat of animals than land. Like land, the geosphere of the waterworld comprising the hydrosphere and the bed below is not uniform.  For instance, the depth of the water varies from a few feet at the shore  to thousands of feet deep at some parts of the deep seas.  There are even places the depth of which goes much  more than the world's highest mountain peaks. With such a varying  depth the surface of the water bed  is also randomly uneven. From comparatively plain basins the  surface of the bed, or the topography, diversifies into hills,  mountain ranges, valleys, craters and some  abysmal trenches.

Quite in line with the land, the temperature of  the waterworld also varies from warm to freezing cold.  Naturally such a variety has helped quite a large  number of life forms to throng this part of the world and  find a suitable habitat for each of them. 

The once mysteries of the vast waterworld have been unveiled a long  while back. Series of explorations under the water and at the bottom of the  seas and oceans has enlightened us about myriads of plants and animals which  have made water their home. Today we know, there is no less variety of marine  creatures than that of the land animals. The size and shapes may be different.  Yet they have a world no less fascinating than the one above. 

Like those on the surface, life under water also needs oxygen  and some sunlight. Oxygen apart, these creatures also need mineral salts  dissolved in water. And the water contains oxygen. It is also rich in common salt.  But in places the other salts that the sea plants and animals must have are scarce.  This is particularly so in warm oceans, where a thin, warm surface layer of water 
floats upon a thick, cold layer. Because the layers do not mix, salts from deep down  cannot rise to take the place of those above used up by plants and animals.  Thus warm oceans usually cannot feed as many living things as cool water can.   Thus, like the life on the surface, water world offers different habitats  for different variety of animals.

Most marine plants and animals live in the upper sunlit layers of the sea.  Here grow the small drifting algae - the green plants that furnish food  for tiny drifting animals. These animals provide nourishment for small fishes  that larger fishes eat. Deep down it is too dark for plants to grow.  It's also colder there. But there are fishes and other animals that feed on  the rain of dead and dying creatures falling from the above. These creatures  find no difficulty in living the way down with an adaptive mechanism  to face a different surrounding.

In the open ocean, plants and animals simply ride the storm waves.  But life is tougher at the sea's edge. Waves pound the shore. Most shores suffer twice daily drying out and soaking from the tides. They are also more open to  attack from heat and cold than creatures of the open ocean.

Let us start our journey to the deep starting from the shores.

the shore liners |the sea world |the freshwater variety