Question

WHY IS THE COLOUR OF OCEANS BLUE

Answer 1

The ocean is blue because water absorbs colors in the red part of the light spectrum. Like a filter, this leaves behind colors in the blue part of the light spectrum for us to see.

Answer 2

The ocean looks blue because red, orange and yellow (long wavelength light) are absorbed more strongly by water than is blue (short wavelength light). So when white light from the sun enters the ocean, it is mostly the blue that gets returned. Same reason the sky is blue."

in another word, the color of the ocean and the color of the sky are related but occur independently of each other: in both cases, the preferential absorption of long-wavelength (reddish) light gives rise to the blue.
thanks I hope u understand