A video camera is a great way to share your diving adventures with others. I have found that a short video clip from a dive trip gets people a lot more excited that some still photos. Seeing a ray fly alongside a reef is just plain cool.
When I decided that I wanted an underwater video camera, I did a lot of looking before buying anything. To get a camera that is made for anything deeper than a swimming pool, you are typically looking at some sort of housing that protects a "normal" camera. You can usually order a housing specific to a camera that you already own. I didn't have a video-capable camera that I felt comfortable taking under water so I bought a package deal.
The first camera that I bought was a simple & relatively cheap Suprema. It comes with a point and shoot camera that is video capable (including audio so you can capture those bubbles). The video quality is decent and it certainly fit my main requirement, which was to show people what I saw. The video ends up being a little jerky if you are trying to capture a long sequence or something that is moving a lot. Some of this is resolved with practice - my newer videos are certainly better than the first ones. No matter what, it just seems kinda hard to shoot video with a little camera in your hands. Gloves make it extra challenging. Still, I am very happy with my Suprema and I like that it just fits in my BC pocket, plus I can still shoot blurry stills if I want to. I like this setup because I can just leave it with my dive gear and it's always there if I need it.
The next step is a housing for your CV camcorder. A couple weeks ago, I jumped in and bought an Equinox HD6 for my Canon HV30. I love being able to shoot HD video underwater. The Equinox is much easier to control than the little point-and-shoot contraption. Everything was easy to use even with my dry gloves on. It has nice grips that make it much easier to pan around. Still, it takes some practice -- I am thinking about trying one of those underwater videographer vacations. There are really only two drawbacks to the Equinox that I have seen: 1) price (although it is cheaper than a lot of custom housings), and 2) convenience - it is big and cumbersome, so you have to go in planning on a video-centric dive.
My Suprema still goes on every trip with me just so I have something if I need it. The Equinox is awesome and I love using it when I can. If you have a big trip planned, I'd highly recommend an Equinox to help you capture some of the fun to share. Or you could invite me and I'll capture the fun for you!!!