Although I am always someone who goes with the cheapest available option for gear, I do like to recognize something that offers good value for money. The Advanced Elements Funk Kayak Bag is an excellent sack to carry all your gear to and from your kayak, and having a few of these cuts down on the back and forth from the campsite to launch point. With 45L each, I like to keep 3 of these in the kayak, one for each hatch.
The bag has a sturdy PVC fabric and robust straps, that will likely never rip apart due to weight, and the zipper will plow shut or open no matter how much sand gets in the way. It's also very easy to wash. The side pocket is not particularly useful. I'm not sure what I would put in there, maybe your sunscreen bottle.
The video below from Advanced Elements gives a good overview of the general aspects of the bag.
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