Polarizer for Zeiss 15mm f/2.8 ZF.2 lens.

Here are two sample shots taken with the Zeiss 15mm ZE (would assume the same results with the ZF.2) in combination with a Marumi polarizer.  As I said, my use of the polarizer on an UW like this does not involve blue sky.  It is to reduce reflections on foliage and water.

Again, expanses of blue sky...not so great.  But in certain situations they are still very useful on UWA lenses.