Shun Cheung , Jul 03, 2006; 10:12 a.m.
This is not a direct answer to your question, but I suppose you are aware that the underwater housings are very expensive. Typically they cost more than the camera body. For example, the Ikelite is $1250: (link) If you actually shoot underwater, there is no other choice besides housings. Otherwise, that is a very expensive and cumbersome way to protect your D70s. Moreover, which lenses do you typically use? Longer lenses may not fit.
For kayaking, a lot of people use Pelican waterproof cases. You put your camera back inside as soon as you are done shooting. Perhaps use some plastic protection bag for water splash. Is that good enough in your situation?
Hopefully, photographers with a lot of Kayacking experience can provide additional ideas.