I have a problem with internal reflections in my dome port.
This is a clean, new Ikelite 8 inch dome port (for Canon 10-22 mm lens).
I took some shots in a crystal clear freshwater pool: some half-in-half-out shots and some very close to the surface. In many of the photos you can clearly see an image of the lens itself (the concentric rings of the lens front elements, or even the lettering on the lens).
It's presumably caused by internal reflections in the dome port.

Is this a well known problem, and are there tricks to avoid it??
In these pictures there was a graduated 2 stop neutral density filter on the lens. Could that be part of the problem?
Any advice welcome
