Transition between subsurface and above surface

[Steve Green]

Hi,

I've been doing a couple of shots recently which involved the camera breaking the surface, slowly.

Now, I have a slight problem where the SSS effect will just disappear to black as it moves across sea level, and I wondered if there was anything that can be done to fix this?

I tried changing the step level, and raising the SSS sea level, but nothing seems to fix it? Anyone else come across this kind of effect?

Thanks,

Steve