zski wrote on Sep 15^th, 2012 at 12:18pm:

Sierra Trading Post has a Columbia Dry Bag Backpack   (You need to Login or Register   (You need to Login or Register   (You need to Login or Register $74.95

If you go with this one, go to retailmenot.com and pick up a 20% off coupon.  That puts the price just below $60.00.  (If you buy other items, you could possibly use a deeper discount coupon, since the current price is right at a break point.) 

I do have a smaller version of this bag which I used as a kitchen pack for this season (e.g., pots, pans, utensils, stove, fuel, reflector oven and other odds and ends).  It has a zip top closure which you can then roll down and buckle if you don't overfill.  I didn't have a chance to dunk it, but did fine with a couple of hard rains and wind.

dd