Fathom SWP 44C is a true wide angle converter for video camcorders. It allows the PWW 200 to zoom through from wide to close up. Fantastic optics for UW usage.
Slightly different is the Deep Epic which uses a large dome port like you would with DSLR housings. One can use Tokina 10-17 or other FE lens. I even used the 4.5mm Sigma full circle FE with it. No limit to what you want to do really as long as the lens works with the port. I personally have made a special port for wide rectilinear lens such as the Nikon 14-24mm f2.8. Red Epic/Scarlet can be fitted with a Nikon mount. Just tested it a week ago on a dive trip. I will show the results at ADEX at the Scubacam booth C10-12.