Post processing
It is important to recognize that the vast majority of images taken under water will come out looking dull and blue. One of the benefits of using a camera with a high dynamic range and the ability to shoot in raw is that we can recover a lot of the color in post.
An example of what a image might look like after post processing compared to before can be seen for example of a whale shark below:
The night and day difference hopefully illustrates the importance of post processing to get images with nice colors. I will eventually get around to posting a more detailed guide on how I process my images in Adobe Lightroom.