Underwater camera

[Captain Kirk]

OK, a bit of background. I'm a whitewater kayaker, and a computer geek. There we go.
Now, I want a camera I can put in the front pocket of my bouyancy aid and whip out when I'm coming to a waterfall etc so I can take photos of people going over them. Therefore it needs to be waterproof.
I've been thinking along the lines of Pentax W10/W20, or the Olympus 720SW/725SW.
Has anyone got any thoughts on either of these 2, or any other recommendations.
Thanks

 

[bigredshark]

I have a pentax WPi, it's not the best but it suits me for skiing, parties and other stuff when my D200 is inappropriate

The newest pentax varient of this should do the job, it's not that quick, not that great quality but it's waterproof and does the job

examples here (sorry it's just party stuff)

http://homepage.mac.com/gary.mackenzie/meninhats

 

[Captain Kirk]

Has anyone got any of the above models? What are start up times like, as I want them to be quite fast as Kayakers don't hang around for long once at the top of a waterfall etc.
Any other reviews on any of them?