I need some advice on Water Resistant, Long-Term camera bags?

I plan on traveling for the next few years throughout the US and Canada, and I need a camera bag that's going to get me through it all. I'll be camping, hiking, swimming, kayaking, spelunking, etc.

Size: I'm a small person (5'3 at 120 lbs) so one of my biggest concerns with shopping for these bags is getting my spine crushed. I have a Nikon camera, 4 lenses, and a tripod. I would very much like to be able to fit a Macbook in the bag when needed, and other things like snacks/sunblock. But I can't deal with a behemoth bag. I'd like something with good structure so it doesn't hurt my back while hiking.

Functionality: I need the best in water resistant materials. I'd rather pay $400 for a bag once than replace thousands of dollars worth of gear. I'm not careless with my gear in the least bit, but I don't want to take chances. I love how the Lowepro Dryzone 200 even FLOATS, but that goes back to my first concern of being too much of a burden to carry. I need something that will last and doesn't scream "I'm full of $$$" (another reason why I lost interest in Lowepro Dryzone 200).

The one I'm currently looking at is Whistler BP 350 AW by Lowepro.
http://store.lowepro.com/whistler-bp-350-aw
It looks pretty good (size-wise), but I'm not sure it's as watertight as I need…

I'd like to be able to give advise based on user experience, but I've never owned a backpack let alone a bag that needed to be water/weather proof.

B&H sells these backpacks that may work: http://www.bhphotovideo.com/...rtclk=sort

Here are a few articles on keeping your gear when kayaking:
http://galenleeds.com/2011/03/27/kayaking-with-your-dslr-how-to-protect-it/
http://kayaking.fredhurteau.com/kayaks-water-and-dslr-camera-equipment-how-i-manage-mine.htm

And I'd check out articles post at outdoorphotographer.com too.

Basically, there are no magic packs that are bigger on the inside. Unfortunately.

For the best in waterproof materials, there are only two choices: Ortlieb and Peli Cases.

Ortlieb does a series of waterproof backpacks (usually specified at IP64 or better), but you'll have to look for a camera insert: https://www.ortlieb.com/en/produkte/rucksack/
They also do a waterproof (IP67) camera backpack that looks just like what you are looking for: https://www.ortlieb.com/en/produkt-details/?produkt=dayshot&list=fototasche&slug=fototasche&clearname=Camera%20Bags
Finally, Peli cases will offer the ultimate in resistance, but are a bit bulkier to carry. And I just see that they also have backpacks: http://www.peli.com/eu/en/products/durable-travel-backpacks/