I have tested this £95 or $125 add on lens with the 4.33" some plus 30 extension on the panasonic GX7 for now just in the sink but results are good and this is very cost effective
Panasonic Lumix G X Vario 14-42mm with Fisheye Converter DMW-GFC1 | Interceptor121 Underwater Photo & Video Blog
Panasonic Lumix G X Vario 14-42mm with Fisheye Converter DMW-GFC1 | Interceptor121 Underwater Photo & Video Blog