A glass of water looks clear,but when we lookout at the ocean,it appears blue.
There are two reasons that cause human eye to see the ocean as blue.
The first relates to how human see light waves coming from the Sun.
The second reason depends on how far away a person is from a water source.
For example, a glass of water appears clear, yet shallow tropical water in the tropics looks turquoise blue.
But the deep ocean looks dark marine blue from far away