When diving in greenish and milky water (the nightmare of every underwater cameraman/photographer!) do not let that this "horrible" environmental condition forces you to resurface without any good picture.
On the contrary, use it to your advantage!
How? I will tell you: if you have an underwater light source with enough power, go and find subjects which are in a strong backlight.
By properly illuminating them with your artificial light and from close range, you will get images with your subject sharp and well exposed but, at the same time, also wrapped in an ethereal and mysterious aura.
A very impressive visula effect!