You have visited Mombasa or any other beach for quite a number of times or maybe you've watched the movies or let's put it simply; you have seen an image of the ocean or sea water appearing blue and you wonder why it appears so yet when you collect it doesn't maintain the color.
Let's get to the explanation of this;
This starts with the sky which appears blue because of the blue rays from the sun which have short wavelengths and are scattered fast and widely after colliding with particles of air in the atmosphere.
The rays from the sun appear dominantly white but produce a number of light rays mainly blue and red. The red rays have longer wavelengths compared to the blue rays.
The ocean, therefore, appears blue because the red, yellow and orange rays which have the longer wavelengths are absorbed more strongly by the ocean water than the blue rays.
According to scientificamerican.com, when the sun rays hit the ocean water, only the blue rays are reflected or returned back to the sky since they are short wavelengths and are hardly absorbed by water.
This effect only applies when the water or pure or rather clear. When the water has algae or mad then the dark or greenish nature of the water will overwhelm the blueness of the water.
People have however made it a notion that the ocean is blue because it reflects the color of the sky. However, the scientificamerica.com explains that the color of the ocean and the color of the sky are related but occur independently of each other.