Niikonos V is Far FAAAAR Cheaper and Easier to come buy for underwater film.
Aquatica made an RZ67 under water housing for 6x7 format RZ Pro II cameras with the RZ Auto Winder installed,
One is listed for sale out of the 50 ever made, see parts list below: offered by Mauricio Handler of NatGeo Fame and association.
Aquatica RZ 67 Housing w/ alarm
Flat port for use with Mamiya 110mm lenses
Dome port for use with 37mm and 50mm
4" port extension ring- add to macro port for using 140mm macro lens.
Internal focus rod and gear.
Package price $4750.00 plus shipping.
If you pockets are deep you can contact mauricio handler <email@example.com>
I cant afford it otherwise I would buy it just to have it and use it, but then thats probably the main reason I cant afford it at this point.
best of luck.