Hmm. I've done underwater filming (Super 8, not still) with a Canon in an Ikelite housing, have attempted to use several Beaulieu S8 cameras in EWA Marin bags for them, and have tried to shoot underwater still with a little Canon point of shoot in an Ikelite housing. I've also used an Eumig Nautica, a self-housed S8 camera.
I couldn't operate the cameras' controls when they were in EWA Marin bags, gave up that effort.
With all of my housings, eye relief is very high. There's the distance from the eyepiece to the housing, the housing's thickness and then the distance from the front of my mask to my eye. I found focusing difficult, composing nearly impossible. The Nautica was the most usable of the the cameras I used underwater.
Get the Nikonos, make sure the o-rings are fresh and properly greased. The alternatives are all much harder to use.