The filter need to be rotated to a specific angle depending of the light direction in order to be fully effective, granted if one could access the rotation of this filter it could be used but to remove which reflections, our beloved environement is pretty low in the reflective scale of things (survival oblige, you wouldn't want to be too reflective and attract predators) and most of the reflection we are faced with are caused by our strobes, again I routinely use a polarizing filter on the lens and slap one on each flashes in top side macro, its great for removing the hot spot on bugs shells, it just seem hard to operate this kind of rig in a underwater housed system, especially in light (pun intended) of the subjects we are face with underwater, most likely a better strobe position would cure the reflection much better than a polarizing filter would.
Cheers.
