Those images are good because the photographer was good, not because of the camera. The light, the composition, the processing.... that's in the hands of the user. I've seen divers pull amazing shots out of cheap underwater point and shoots. But then I did most of my dive training with a photo major so maybe my experience was a little different than others.
My favorite brand is
Sealife cameras. They cost about the same as a good underwater housing for a point and shoot. And the buttons are a heck of a lot easier to use in the water than with many housings.