The K-7 body and the Pentax DA WR and DA* lenses are weather resistant. That is not waterproof, but there have been many experiences of pentaxians who used the K-7 with WR lens(es) in rain without any problem.
I have myself a K-7 and two non-WR lenses, although one (Nokton 58mm) is very robust and almost WR. I use my K-7and lenses outdoor and I took them a number of times in wet, dusty and muddy conditions. I had no problem, but off course I take care of the gears.
In response to your query, splahes should not be a problem but I would not leave the camera and lens(es) sitting in the water at the bottom of the canoe. I used before my cameras on the water (sea, lakes, rivers) while on canoe, dinghy or small boats, and I strap the camera around my neck all the time. When I did not use the camera, I put it inside a small rain jacket to be protected, with the strap around my neck. In a few occasions, I was even wearing my wet suit because of the cold and damp weather conditions and I was wearing a light rain jacket on the top just to protect the camera. Off course the camera and lens got wet, and I wiped them regularly beftween series of shots.
Hope that the comments and experience will assist.
Note that there have been a number of recent threads on WR in
www.pentaxforums.com.