Thanks so much for your reply. Wish you all good in your moving.
Yes, I just decided to buy a Sigma 15mm which is more newer than Tokina 10-17. I'm with a D750 now and in the process of purchasing a Nauticam housing system from China. I just read an article online yesterday saying that Tokina 10-17 works very well on a full frame DSLR with a more like wide angle effect than fisheye on DX camera. I attached the link here https://www.uwphotographyguide.com/sigma-15mm-tokina-fisheye-review for you, may be you have some interest in it. By the way, on your experience, do you think it's better to change for a new D850 instead of using the current D750 which seems to be much more harder for sell when I want to upgrade my devices in the future.