If you are only going to use this for Back up safty and to help out with manuvering at the dock do yourself a favor and go Black and White. Not only is it MUCH cheaper but you will also be able to see it in the daylight. Rosen makes a water Resistent screen. It is no longer a current product but you may still be able to get some. I also sell a screen from a company called Crestron that is not sensitive to light but as you can imagine the cost goes up. They also make a waterproof membrain so you can protect it. If you go with Crestron the options are endless as it is a full remote control system if you want it to be. For examply you could have presets for drives and stuff like that

Let your mind go wild and the Crestron will do it....... All it takes is money

If you go black and white however you would stay cheap and compact. Camera's now are so damn small that you will not even see them on the boat and you can find a ton of them that will work with 12 volts. If you are worried about theft then Pioneer makes a screen that pops out and is also good in the light.
Jon