The answer on underwater cameras depends on whether you are a snorkler solely or do scuba also.
It also depends on your budget and what your goal is with the photography and how deep you go.
As you go deeper, you lose light starting with the longer wavelengths first. At 15' you lose the reds. A lion fish's red markings look black even in pretty "shallow" water. To get the color back, you need to use a strobe. It is best to use an external strobe because the camera's strobe will light up in particles in the water and cause "backscatter" which is not good. A strobe off to the side will light up the particles also but the light comes back to the light source.
Since white balance is critical in underwater photography, you will want a camera with at least RAW capabilities. This means using only the most advanced point and shoots or a DSLR.
There really is no such thing as an "underwater" camera. You buy a camera and get a housing to protect it. The housings almost always cost more than the camera and sometimes quite a bit more.
For a good point and shoot system with camera, external strobe and housing, you are doing well to get it at just over $1,000. For a high end housing, you can easily go over $2,000.
A DSLR system will go for around $4,000 for a not high end system. It gets expensive.
You can get a less capable point and shoot with no external strobe and with just JPEG capability for far less.
