I carry one of these in one of the pockets of my PFD which I always wear when in the canoe. I have added a small key chain pill container in which I packed a vasoline impregnated cotton ball for fire starting. Nothing catches a spark quite like it, even when wet:  
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After the posts here about anchors and drift socks, both of which I use, I put one of these on the outside of the PFD where it is readily accessible in case I need to cut a line:
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After reading this I'm seriously considering adding a larger, fixed blade knife and a space blanket.

Pat