Making your own housing can be alot of fun, but it is guaranteed to be a is a heck of alot of work. That's how I made my first housing. For lots of folks however, they don't have the time, or the tools, and thier parents won't let them get the entire garage full of fiberglass dust and epoxy fumes.
Here is another option. http://www.chacconne.com/DM_Info.html
I happy to give advice to any one seeking to get thier camera or video camera in the water.