From your links, I guess you are looking for waterproof cameras?
Just want to let you know - these "waterproof" cameras are really only
"splashproof".
True they are "waterproof" (ie. can be completely submerged in water for a certain amount of time) for the first few months, but from what I read in camera forums, the water seal of the door that covers the battery / memory card / USB cable socket / charging socket will eventually fail. Many people start to notice water inside the door, and some blame this for their camera eventually failing.
Remember, you must open this cover door every time you transfer your pictures and charge your camera, therefore its seal is an inevitable wear-and-tear item.
Also, the deeper in water you go, the greater the pressure and the more likely water may seep in.
Therefore you should really use these as "splashproof" cameras (ie. not totally submerged into water). Some people claim that sealing the door with
duct tape helps, but that sort of defeats the purpose of a waterproof camera! Some also claim that buying one of those
silicone camera skin that envelopes the body including the cover door may also help, but I have no experience with this claim. The silicone skin may also help with your grip on the camera when it is wet.
If you go diving (even snorkeling) into deeper water, you probably need true waterproofing of the camera. You should buy an
underwater camera hard case - these are usually designed specific to the brand and model of the camera. They easily cost as much as the camera itself, and they are bulky. They also won't last forever but many have replacement seals you can buy.
There are cheaper
soft underwater cases which can accommodate different brands and models of cameras - the major problem is that under water, the pressure compresses onto the soft case against the camera, making operating the buttons on the camera difficult. Also you may find it difficult to take it into greater depths, because it is too light and floats. It may work OK in shallow water like 1-2 feet (I don't dive or even snorkel therefore I dunno what depth is ideal).
------------------------------------------------------
OK going back to your choices .....
Take a look at this camera review:
Waterproof camera group test
Both Pentax and Olympus have been producing "waterproof" cameras for some time, and their (initial) weatherproofing quality is good (but as I said, it is only a matter of time and frequency of use). I don't own a weatherproofing point & shoot camera therefore I don't know their longevity in terms of waterproofing.
The optical quality of both cameras are good but not the best compared to eg. Canon. If you use the camera on the beach in sunny condition, most cameras give you good picture quality.
If you take it deep under water with less light, you need a camera with good light sensitivity (ie. good "high ISO performance"). You may need to boost the sensitivity to ISO 400, 800 or even higher. Unfortunately both the Pentax and Olympus (the latter more so) are not so good in this area (but neither are most of these point & shoot waterproof cameras). I don't believe you should take any waterproof point & shoot camera into great depths anyway.
Some general tips:
"Megapixels" does not always mean better quality (particularly for small point & shoot cameras). The megapixel count only really matter if you intend to make large paper prints of the pictures.
If you intend to view your pictures on low resolution devices such as your camera, your computer screen or your digital photo frame, then you don't really need any resolution setting higher than 6 MP (actually more like 3 or 4 MP).
"The number of X" power of the zoom lens does indicate the range of zooming, but you need to know what the starting (wide angle end, the lower number) and finishing (telephoto end, the larger number) levels are.
Most of these compact cameras have non-standard (ie. not referring to 35mm cameras) focal lengths such as "2 - 11.5mm", which makes not much sense on their own. You need to
google the camera's specification to look for the focal length range in terms of
35 mm camera standard.
For the wide angle side, a starting point of 28-35 mm is good. For telephoto, around 100-120 mm is also good (I don't think these waterproof cameras have long telephoto range anyway). Some lens are designed more for wide angle shots and some not, it depends on what you want to shoot (scenery, candid bikinis or topless .....)