Why my images appear bluish and do underwater mode helps?

[Limoges Diver]

The underwater mode basically does what photoshop does. It changes the white balance to enhance the reds and cut down the blues. It's meant for underwater for a reason. Most of the time, Photoshop can fix the color balance, but that get's limited after about 30 feet or so depending on the visibility.
Strobes are the only real way to go to get real color correction though...

I find that colour balancing is not the true solution, because it doesn't get as much real colour as with channel mixing in Photoshop.
The process is quite simple once you get the hang of it:
1) adjust blue and green levels; 2) mix the channels to the red channel: add green, and remove blue. 3) adjust red level with the mid-point adjustment slider; 4)adjust that saturation of the various colours (red, green, blue, yellow, cyan and magenta), then set that adjustment layer to "multiply" and then adjust the opacity to a level that looks best. Her is the result of that process on a picture I took in Cozumel at about 40 feet depth, on an overcast day:

here is that precess done to one of the images above:

original:

after this process:

 

[DevonDiver]

As Limoges Diver said, channel mixing has a dramatic effect. I use Photoshop for this and 8/10 times it turns a blue washed-out image into something useable.

If you search youtube, you will find several decent video tutorials on how to post-edit your underwater pics. YouTube - Photoshop: Underwater color correction

 

[Limoges Diver]

As Limoges Diver said, channel mixing has a dramatic effect. I use Photoshop for this and 8/10 times it turns a blue washed-out image into something useable.

If you search youtube, you will find several decent video tutorials on how to post-edit your underwater pics. YouTube - Photoshop: Underwater color correction

That's the video I learned from! I forgot that I found it on youtube. I wold like to see other methods for correcting images, because this system doesn't always work.