It would help to know what camera you have. You can buy custom housings for not much. I have a Sony DCR-P100 digital video camera and I bought the $200 housing for it. With the controls, I take digital still and digital movies with it. I bought the 1 gig memory card and can video 40 minutes of video, so depending on your dive time, that may cover the whole dive.
For something strange though, I gave this some careful thought a long time ago for a generic video housing, but never tried it. You could buy an Otterbox ($12) which are supposed to be good to 100 feet.
Here is what the website says:
"OtterBox have been tested to 100 feet and should not leak if cared for and used properly."
You have to only want the video only, turn the video on, have the lens toward the clear bottom of the housing, close the Otterbox and dive. You would video the whole dive, but would have no control over starting, stopping, and switching to camera mode. I imagine you would need the big memory card.
Again, this was only a theory, never tested, that I was toying around with. Best of luck to you.