Like said, a camera pack is useless for carrying camping gear, but certainly not the other way around. To keep things light I just wrap lenses in spare clothes, if hiking in a rainy place also in a SeaToSummit silnylon waterproof pouch, which I use also for clothing and sleeping bag. They weigh very little and save space (I replace the sleeping bag stuff bag with a 20 liter STS bag also). Camera with "standard lens", whatever it happen to be, i just have hanging by my neck, or thrown on the top of my pack, which is usually flat enough to hold it. If it does not, there is the neck strap.
Kayaking and backpacks do not really fit together at all, you need watertight stuff sacks which are small enough to fit inside the cargo holds. You rally can have only one camera out, and if it is not in a watertight underwater enclosure it will be ruined if you take a dip. So the only practical way is to have the camera in a watertight pouch and just unwrap it for each photo-op, which is clumsy and slow, or take your chances and have it out at all times (it will get wet from the water dripping form the paddle). How dangerous this is depends on the stability of the kayak, your proficiency at kayaking and the wave conditions. Canoeing is quite a lot safer, drier and more convenient for a photographer, by the way. And easier to pack.