Manual White Balance
On land we don’t think about the white balance it is factory set to auto. But underwater you either need a red filter or you need to adjust the cameras’ white balance. This basically means you are telling the camera what white is. It is easier to go through your camera’s process on land first without the housing. You will need to go into your camera menu to find the WB settings. If your camera does not have a manual adjust setting then the best you will be able to do to correct the colour underwater is check to see if there is an underwater or fish setting and try that. (or add a red filter)
In your cameras’ manual white balance (MWB) setting – Point the lens at something white or near to white, it will need to fill the view from the lens. Take a photo, the camera will use this as a measure. It will ask you to ‘Save it?’ so save it. Now you have reset the white balance. Try it on non white surfaces and see what happens! It will look weird on land.
When you are confident you know what to do fit the housing on and continue practicing. Remember it is always harder underwater.
To adjust it underwater you will probably need to buy a white marker board designed for use underwater. They usually come with a pencil and clip and are not expensive. It is also possible to get good results by using the palm of your hand or even the sand.
You will need to re-calibrate the white balance when you change depth every + or – 30ft (10 meters) so don’t start to adjust until you are at the depth you will be diving at. In other words don’t calibrate it on the way down or near the surface. When the sun goes behind a cloud this will make a difference too. You will need to re-set (calibrate) the WB throughout the dive but this does give very good results and works better than adjusting it on your laptop.
If you point the camera on a subject try to have the sun (the major light supplier) behind you so it illuminates the subject. This principle works for video too as does the manual white balance adjusting. Your camera may have an easy access button that you can assign to MWB so you don’t need to go into long camera menus all the time.