Alot depends on the type of water you will be kayaking and if there is a chance of flipping. How much shooting you will be doing also will factor in. I carry my D300/18-200 combo frequently while kayaking lakes and swift rivers. I don't worry so much about flipping as I do rain, spray, and water dropping from the paddle. I use a waterproof backpack that sits on the floor in front of me unzipped, that's there the camera lives. It is easily accessible as most shots aren't set up and happen pretty quick. I can zip it up if paddling through rougher water or a sudden unexpected rain storm (happened on the White River in Arkansas). I don't plan on flipping, but that's a chance I take for connivance.