Here I am late, but with advice that will make your loan company very happy!
I use a Nikon F100, but the less expensive versions you mentioned seem to work just great u/w! But here is my (costly) recommendation:
Nikon Camera
Nikkor AF 35mm-70mm D zoom lens
Subal Housing
Subal Dome DP-SWP
If Sea and Sea makes the same combination and you like it better, go for that.
The crux of my recommendation is in the zoom lens. After setting up the Nikon with my 60mm Micro=Nikkor, along came a school of Coronetfish, hunting in a "pack": it looked like a missle attack! Then, of course, I put the 20mm Nikkor on and spot a wonderful group of ghost shrimp that would take up 10% of the negative area.
These events and many other similar to them finally convinced me to give the zoom a shot. What a difference! The 70mm end of the lens works perfectly for nearly any macro shot. The 35mm end is nearly perfect for all those grand coral/gorgonian scenary shots along with those of schooling fish and the large pelagics that cross my path. As far as I can tell, the quality of the zoom optics is similar to that of the fixed focus lenses--excellent. If I had to do it all over again, I would have just purchased the zoom!
Cost?
Camera--$600.00-$1200.00 (New York Mail order prices)
Lens--$670.00(ditto)
Housing--$2750.00
Port--$620.00
Diopter for the lens--$30.00
Grand total = $4670.00-$5370.00!
Did you say that you really just wanted a point and shoot?!
Scorpionfish--a kinder, gentler, POORER Scorpionfish