As mentioned previously the size of the camera is a real consideration when breath hold diving. But don't forget that the underwater housing and lens make a huge difference as well. Ideally you want a 3 chip camera but more importantly you need to be able to adjust the white balance while it is in the housing. Many of the consumer type models have touch screen white balance control which cannot be adjusted in the housing. That said I do a lot of stuff with a single chip camera in a Light and Motion housing and in shallower, clearer water it's fine. Check out Carlos Coste's dive at
http://www.underwaterpics.co.uk/2005gallery/videos
The stuff at the begining and end of the dive is shot with a Sony PC330 single chip camera with automatic white balance. The deeper shots at 50metres are shot on a 3 chip camera with the white balance nicely sorted. The 80m plus stuff is filmed on an ROV with a very basic annalogue camera.
Red filter is essential deeper than 10m to put the colour back in but you need to take it off nearer the surface as you get too much red. If you are looking for near broadcast quality you need to look at the latest 3 chip cameras with HD and true widescreen.
One last point, having the best kit does not guarantee the best footage. There is a lot of skill involved too. I always say if you give an average joe a canvas and some oils you don't get the Mona Lisa!
