I was thinking about an inexpensive camera. I did a search on
dpreview, and found Ricoh G600, which was watreproofed according to
JIS grade 7. This means that the camera can stand 30 minutes at a
depth of 1 m, http://www.opticsplanet.net/water-proof.html . Perhaps,
it could withstand larger depth ? It probably could do it, at a
stretch. Or not ?

What this means in real world is that you can probably take the camera
out in the rain... If you're lucky, maybe even a heavy rainstorm...

Correct

Here is the camera Olympus Stylus Tough 8000, which is rated JIS grade
8. This means that it can be continiously immersed into the water at
the conditions more severe than the camera above, JIS grade 7. The
description of Olympus says that the camera is waterproofed up to the
depth 33 ft, or 10 m,
http://www.digicamera.com/reviews/olympus_stylus_8000/ . This is what
I need !

Which means that you can take it in the bathtub with you...

I don't know about the Tough 8000, but my Olympus Stylus 1050 SW is
specifically designed for snorkeling. It's particularly good for taking
underwater shots of those bathing beauties you're so fond of watching in
North Florida springs.

If you are only going to be taking a few photos, you might want to
consider an older film camera and housing... Some underwater
photographers are switching over from film to digital and you can
sometimes get really good deals on the old cameras and housings...

I really, really, really recommend against a film camera for someone just
starting underwater photography. For the first year or so, the ration
between keeper and garbage pictures is quite low. Developing and printing
are not cheap. The high cost for a low return has turned many a photographer
away from taking underwater shots. With digital, the shots you don't like,
don't cost you anything.

If you're willing to settle for the point-and-shoot type of digital
cameras, your best bet is to just look for housings that are acceptable
in price and then buy the camera that goes with it... Otherwise, you
might get a camera that no one makes a housing for or if they do, it is
overly expensive...

A pretty good idea, actually. In most cases, the housing will be good to
greater depths than snorkeling cameras like mine. Those that may consider
diving one day should consider this option carefully. The downside is that
the combination of camera and housing, even for the point and shoot models,
is likely to be more than the better quality waterproof options. If all
you're going to do is snorkel, you get more bang for your buck with a
snorkeling camera.

As far as megapixels go, you don't necessarily need 10+mp unless you are
going to be doing significant cropping or enlarging the photos to poster
size or better... If you are just going to post them on a web page, even
a 2mp camera will produce images larger than most monitor resolutions...

Correct.

Lee