Question

Existence of water is one thing, its availability to living beings is another, briefly explain this.

Answer 1

Yes, both are different thing.

We know that

Water is occuping the earth space upto 70%.

Now only 2% of it is drinkable. Remaining water needs to get processed then it will be available for us.

For example,

Ocean has a lot of water but due to high salt and mineral level can't drink.

some times water is in compound form with other elements and we can't use it.

But on the other hand,

2% of total water in the world means river, lake are the source of drinkable water.

Availability and the existence both are different thing.