For photography, forget the filter unless you are diving fairly shallow, only a few meters and do so at a constant depth. Filters are depth dependent, the amount of filter needed is directly linked to the depth you are at and to make matters worse, it does not "add" red back but rather reduced the amount of other light colors available which has the effect of reducing the already low amount of ambient light. No one filter will be correct at more than one depth and as depth increases, so does the need for more filtering. Only by learning to use color balance correctly can you do an adaquate job of restoring color without adding a strobe....which is the best option. For topside photography and snorkling, filters have their use, underwater, proper camera operation and strobes are the best options.