The fish eye conversion lens is interesting. Are you referring to the Panasonic DMW-GFC1? If that's the one, then I don't think it's wide enough because it only give 120 degree on land, and would become 84 degree once in the water. May be a wet wide angle lens is a better solution, just don't know which wet lens work.
Yes the conversion lens is the DMW-GFC1. I am by no means an expert but this combo is ok for semi-wide. I would guess its more than 84 degrees FOV when using the 3.5" dome port underwater. I would guess its at least 120 degrees.
I bought the 14-42X lens a long time ago , hoping that i would be able to use the zoom function. However looks like there is now a Nauticam gear for this function..
(Sorry for discussing WA in a macro discussion. Just wanted to highlight this lens can be used at both ends!)