I am using the Nikon 16-35 on FX with a large Dome port now (Subal DP-230). Albeith this is a good and handy lens for underwater usage, I'm still looking at the 14-24 f2.8 for its better IQ especially at the wide end. And yes, I am aware that this lens is some 325 grams heavier than the 16-35.
Going soon to Cocos for large pelagics and eventually will switch to the 14-24.
Is there anybody with same or similar configuration having real underwater experience with this lens? I did a search here but did not really find much...