I do floats ina solo canoe and that can have little more room in it than a yak. But I do try to approach the whole thing like I was backpacking. If on more than an overnighter I don't take things that need to be refridgerated. With the exception of maybe a couple of steaks that have been frozen. Wrap in a little newspaper, plastic bag and then a towel or 2 and some clothing. Makes a great 1st night campfire meal and will keep a couple of days like that in cool weather. I also often take fresh veggies like corn, carrots, beans, and potatoes. They will keep fine just open in the boat. I do take canned goods. If you want alcohol enjoy bourbon instead of beer. It packs better. For water I usually go to the grocery and get one of those 2.5 gal spring water cubes with a spigot and a handle. Doesn't take up much space and is very convienient. I actually use these alot when camping either out of a vehicle or canoe. I also carry 2 Kleen canteen SS water bottles. This pic is from a fully loaded 4 day float a couple of years back. Tent, self inflating sleeping pad, sleeping bag, backpacking stove, clothes, tackle bag, 3 rods. I have a double milk crate that fits behind the seat which holds the above mentioned water and canned good and any loose stuff I might carry. 12' canoe.

I'm thinking of trying one of the new collapsible tent cots for my sleeping quarters. This should be nice on rocky gravel bars.
http://store.kamprite.com/catalog/Ka...C-p-16138.html
Probably more than you asked for but I take stystem approach to boat packing.
KISS Principle = Keep It Simple Stupid.
Your best defense against Murphy's law!