Nice images! I used the 8-15mm with my 4 inch Zen dome and loved the results. According to the Nauticam port charts you need a 30mm port extension with the the Nauticam 4.33. As always I'd double check with one of our sponsors before any purchase. Some of the Zen domes have changed their length over time like the DP100. Better to check to make sure of the correct extension.
Thanks a lot Steve. I'll have to investigate the 8-15 some more. My wallet has been too full lately. The 8-15 may help with that.