IMHO Olympus can produce cameras with great freatures but poor image quality. I'd go for the water resistant Canon, Pentax or Panasonic if I were you. The Canon would be my choice, but for the relatively narrow wide-angle, which is what you want for outdoors photography (35mm). The Panasonic has a 28mm wide angle, which is better. The Pentax W60 and W80 both have a good focal length range, but have a very sorry 175-200 shots per set of batteries, which would completely rule them out for me. The Canon D10 also has a range of 220 shots form a single set of batteries, making the 300+ you get from the Panasonic look really good. Finally, the Canon is waterproof to 10m, the others 3m, which is a major difference.
SO, in summation:
Canon D10
Pros: most waterproof/toughest, highest image quality (shared with Panasonic)
Cons: not wide-angle (35mm), comparatively few shots for batteries, chunky.
Panasonic TS1
Pros: most shots from batteries, best focal length, compact
Cons: less sturdily built
Pentax:
Pros: good focal length range
Cons: not enough battery life, crappy flash and not as sturdy as the D10.
For me, if I was a snorkler or a kayaker, the D10 would be a no-brainer, otherwise I'd go for the Panasonic.
Have a look at this too:
http://www.dpreview.com/reviews/Q209waterproofgroup
All good things are wild, and free.