As aready written by many,
this reflection comes either from:
- the sunlight hitting the front of your lens (painting the front of your lens with a black sharpie eliminates this)
I had this with most of my housings(Ikelite, Hugyfot,Nauticam as it depends on the lens, not on the housing.
Compact cameras with big, silver front of the lens are prone for that, my DSLR lenses are doing it less as they are usually all black
- stray light from the internal flash (black gaffer tape helps with that), my 1st housing Ikelite for Fuji E100 had to be taped off to avoid this problem)
- some/all ikelite ports where/are still made of tranparent acrylic material and this let the strobe light sneak in and provokes the reflection) (Gaffer Tape helps but looks cheapo)
You usually should not use any filter on your lens, they create more problems than are helpful.