In the hands of a relatively experienced diver, using a red filter and manual WB at the touch of a shortcut button, I have seen the S100 and S95 produce some reasonable video. It does well in low light and surprised me with it's output. It won't produce the hi end video that much larger and more expensive set ups do, but it is great for the money you spend. It's a great starter and the wide angle lens can wait until your friend gets into it more.
A great starter for video and good for stills to mix it up too.