A favorite among U/W photographers is the Fisheye lens option and for the Sony A7R II, I tested the ALL MANUAL Rokinon 12mm F/2.8 ED AS IF NCS Fisheye for Sony E-mount. I used this lens with the new Ikelite Sony A7R II TTL housing, the up to 2.8 inch universal gear (included with the housing along with a second up to 3.0 inches gear) for focusing the lens using focus peaking, a very short port extension and the Ikelite eight inch dome port. Prior to the dive I set aperture at F/9 and used shutter speed and ISO to control exposure. I also used two Ikelite DS 161 strobes set to TTL along with two dome defusers. I think a smaller diameter port configuration could be supported using perhaps a 140 mm dome port. The eight inch port worked across a wide range of subjects but is not ideal for very CFWA. This lens is also branded as a SamSung and perhaps others, it is quite sharp and works well out of the water for such things as astro photography.