Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
The lack of zoom means lack of real macro that means nobody will do a housing
I don't understand who would be interested in spending 3000 on a compact camera with no zoom
I think you make confusion between SLR camera with changeable lens and compact cameras with fixed lens. In a compact camera only zooming allows for magnification with a close up lens and the reproduction ratio is nowhere near what a full or cropped sensor SLR can offer. The RX-1 has a 35mm lens with a close up lens you would end up crashing into the subject pretty quickly assuming it can actually focus at few cmI used to get wonderful macro photos with a prime (non-zoom) 50mm lens. Canon makes about a half dozen prime lenses, two of which are "L" lenses (professional photography grade).
"Zoom" has nothing to do with macro, and in fact, limits the aperture. It's one of the least important elements to an underwater camera system in my layman's opinion. Now, if we're talking about taking photos of football players, or racecars on the track, then zoom is a bit more important .
I'd prefer a fast prime with good glass to a slower zoom, or a zoom with mediocre glass any day of the week, but I'll agree that 3k for a single-lens is a little steep.