Question

why the water in glass appears white or colourless and ocean water blue?

Answer 1

The ocean water actually reflects the sky so it appears blue.

Answer 2

Water in a glass appears colourless but appears blue in the ocean because the water in a glass is usually purified and it reflects the colour of the light source.
I mentioned purified because ocean water contains a bacteria called cyano bacteria which gives water its blue colour and yes the ocean water reflects the colour of the sky which is blue in colour.

I hope this helps you.


Remember a very important thing water is never white it is colourless.