Keep in mind that the Nikonos V is a discontinued product:
Originally Posted by photobum
You can purchase a new NikV body for $400, or used (from B&H) for $250. A 35mm lens should set one back about $50.
Here are some things to consider--
DOF is a big deal in UW photo. If you are in the pool, you will be moving unless you weight your self down. Even then bouyancy will mean your arms are moving. So, you need fast shutter speeds. Your subjects are moving. So, you have fast shutter speeds and you will have problems making critical focus, so you can't really shoot wide open. Also, you will be using equipment you are not familiar with (and is not fast to use anyway) So, you will likely be using fast film and shooting zone focus.
You may think that MF would allow for better quality, but under these conditions, the lower DOF will likely hurt you. UW photographers are happy with digital (crazy people) in part because the sensors are smaller, so they are using shorter focal length lenses and getting more DOF.
The advantage of a housed camera is that you can adjust focus. With MF, it will be slow, though.
Now, here is where it can get tricky. The focus distance shifts above water and below for the 35mm lens. I.e. if you set your lens to focus at 3' above the water, it may be only 2' underwater. So, if you are moving above/below the water, this will be a problem.
Keep in mind that a NikV (and a Sea and Sea, I believe) is a viewfinder camera--not a rangefinder. You set the focus on the lens and shoot. Given the focus shift for a 35mm lens underwater, this can be fun.
When I have used my NikV in the pool, I used 400 speed film and shot bascially zone focus. You could probably get by with 100 speed, but I was going for maximum number of in-focus shots.
So, here are recommendations
1) A Nikonos camera with a 35mm lens. This is a really nice lens for sharpness. Underwater it acts more like a 50mm lens.
2) A Nikonos camera with a 20mm lens. This will allow you more DOF and more good shots underwater. Keep in mind, the 20mm is *only* usable underwater. It is also a lot more money (like almost 10x used).
3) you can find a Nikonos IV for cheaper than a NikV. The reason is that you don't have manual control. This makes for a nice canoe/kayak camera as well as a pool-camera, but is limiting.
4) A Nik III is all-manual. They can be had somewhat cheaper than a NikV.
5) The Nik II is even cheaper. There are rumored to be some problems with the design, so it can be difficult to work with.
An option are the "Sea and Sea" line of cameras. These are fixed lens cameras (but you can get attachments for the lenses to make them more WA, if you like). One of the great bargains out there is the "Hanimex Amphibian". This is basically the first Sea-and-Sea under a different name. You can find these for under $50 (and often under $30). They are basically a point-and-shoot type camera built into a dedicated housing.
Hope some of this may help.